Let-up (lĕt"ŭp`) noun [ See Let to forbear.] Abatement; also, cessation; as, it blew a gale for three days without any let-up . [ Colloq.]

Lettering noun
1. The act or business of making, or marking with, letters, as by cutting or painting.

2. The letters made; as, the lettering of a sign.

Letterless (lĕt"tẽr*lĕs) adjective
1. Not having a letter.

2. Illiterate. [ Obsolete] E. Waterhouse.

Lettern (lĕt"tẽrn) noun See Lecturn .

Letterpress (-tẽr*prĕs`) noun Print; letters and words impressed on paper or other material by types; -- often used of the reading matter in distinction from the illustrations.

Letterpress printing, printing directly from type, in distinction from printing from plates.

Letterure (-ur) noun Letters; literature. [ Obsolete] "To teach him letterure and courtesy." Chaucer.

Letterwood (-wod`) noun (Botany) The beautiful and highly elastic wood of a tree of the genus Brosimum ( B. Aubletii ), found in Guiana; -- so called from black spots in it which bear some resemblance to hieroglyphics; also called snakewood , and leopardwood . It is much used for bows and for walking sticks.

Lettic (lĕt"tĭk) adjective (a) Of or pertaining to the Letts; Lettish. (b) Of or pertaining to a branch of the Slavic family, subdivided into Lettish, Lithuanian, and Old Prussian. -- noun (a) The language of the Letts; Lettish. (b) The language of the Lettic race, including Lettish, Lithuanian, and Old Prussian.

Lettish (lĕt"tĭsh) adjective Of or pertaining to the Letts. -- noun The language spoken by the Letts. See Lettic .

Lettrure (-trur) noun See Letterure . [ Obsolete] Chaucer.

Letts (lĕts) noun plural ; sing. Lett (lĕt). (Ethnol.) An Indo-European people, allied to the Lithuanians and Old Prussians, and inhabiting a part of the Baltic provinces of Russia.

Lettuce (lĕt"tĭs) noun [ Middle English letuce , probably through Old French from some Late Latin derivative of Latin lactuca lettuce, which, according to Varro, is from lac , lactis , milk, on account of the milky white juice which flows from it when it is cut: confer French laitue . Confer Lacteal , Lactucic .] (Botany) A composite plant of the genus Lactuca ( Latin sativa ), the leaves of which are used as salad. Plants of this genus yield a milky juice, from which lactucarium is obtained. The commonest wild lettuce of the United States is Latin Canadensis .

Hare's lettuce , Lamb's lettuce . See under Hare , and Lamb . - - Lettuce opium . See Lactucarium . - - Sea lettuce , certain papery green seaweeds of the genus Ulva .

Letuary (lĕt"u*a*rȳ) noun Electuary. [ Obsolete] Chaucer.

Leuc- (lūk-). Same as Leuco- .

Leucadendron (lū`kȧ*dĕn"drŏn) noun [ New Latin , from Greek leyko`s white + de`ndron tree.] (Botany) A genus of evergreen shrubs from the Cape of Good Hope, having handsome foliage. Leucadendron argenteum is the silverboom of the colonists.

Leucaniline (lu*kăn"ĭ*lĭn or -lēn) noun [ Leuc- + aniline .] (Chemistry) A colorless, crystalline, organic base, obtained from rosaniline by reduction, and also from other sources. It forms colorless salts.

Leuchæmia (lu*kē"mĭ*ȧ) noun [ New Latin , from Greek leyko`s white + a"i^ma blood.] (Medicine) See Leucocythæmia . -- Leu*chæm"ic (lu*kĕm"ĭk) adjective [ Written also leukæmia , leukæmic .]

Leucic (lū"sĭk), Leu*cin"ic (lu*sĭn"ĭk) adjective (Chemistry) Pertaining to, or designating, an acid obtained from leucin, and called also oxycaproic acid .

Leucin (lū"sĭn) noun [ Greek leyko`s white.] (Physiol. Chem.) A white, crystalline, nitrogenous substance formed in the decomposition of albuminous matter by pancreatic digestion, by the action of boiling dilute sulphuric acid, and by putrefaction. It is also found as a constituent of various tissues and organs, as the spleen, pancreas, etc., and likewise in the vegetable kingdom. Chemically it is to be considered as amido-caproic acid.

Leucite (lū"sīt) noun [ Greek leyko`s white: confer French leucite .]

1. (Min.) A mineral having a glassy fracture, occurring in translucent trapezohedral crystals. It is a silicate of alumina and potash. It is found in the volcanic rocks of Italy, especially at Vesuvius.

2. (Botany) A leucoplast.

Leucitic (lu*sĭt"ĭk) adjective (Min.) Containing leucite; as, leucitic rocks.

Leucitoid (lū"sĭ*toid) noun [ Leucite + -oid .] (Crystallog.) The trapezohedron or tetragonal trisoctahedron; -- so called as being the form of the mineral leucite.

Leuco- (lū"ko-), Leuc- (lūk- ). [ Greek leyko`s white.] A combining form signifying white , colorless ; specif. (Chemistry) , denoting an extensive series of colorless organic compounds, obtained by reduction from certain other colored compounds; as, leuc aniline, leuc aurin, etc.

Leucocyte (lū"ko*sīt) noun [ Leuco- + Greek ky`tos a hollow vessel.] (Physiol.) A colorless corpuscle, as one of the white blood corpuscles, or those found in lymph, marrow of bone, connective tissue, etc.

» They all consist of more or less spherical masses of protoplasm, without any surrounding membrane or wall, and are capable of motion.

Leucocythæmia Leu`co*cy*the"mi*a (lū`ko*si*thē"mĭ*ȧ) noun [ New Latin , from Greek leyko`s white + ky`tos a hollow vessel + a"i^ma blood.] (Medicine) A disease in which the white corpuscles of the blood are largely increased in number, and there is enlargement of the spleen, or the lymphatic glands; leuchæmia.

Leucocytogenesis (- sī`to*jĕn"e*sĭs) noun [ Leucocyte + genesis .] (Physiol.) The formation of leucocytes.

Leucoethiopic (- ē`thĭ*ŏp"ĭk) adjective [ Leuco- + Ethiopic .] White and black; -- said of a white animal of a black species, or the albino of the negro race.

Leucoethiops (-ē"thĭ*ŏps) noun [ Leuco- + Aethiops .] An albino. [ Also written leucœthiops .]

Leucoline (lū"ko*lĭn or -lēn) noun [ Leuc- + Latin ol eum oil.] (Chemistry) A nitrogenous organic base from coal tar, and identical with quinoline. Confer Quinoline .

Leucoma (lu*kō"mȧ) noun [ New Latin , from Greek ley`kwma , from leyko`s white.] (Medicine) A white opacity in the cornea of the eye; -- called also albugo .

Leucomaine (lu*kō"mȧ*ĭn or - ēn) noun [ Leuco- + -maine , as in ptomaine .] (Physiol. Chem.) An animal base or alkaloid, appearing in the tissue during life; hence, a vital alkaloid, as distinguished from a ptomaine or cadaveric poison.

Leuconic (-kŏn"ĭk) adjective [ Leuc- + croc onic .] (Chemistry) Pertaining to, or designating, a complex organic acid, obtained as a yellowish white gum by the oxidation of croconic acid.

Leucopathy (lu*kŏp"ȧ*thȳ) noun [ Leuco- + Greek pa`schein , paqei^n to suffer.] The state of an albino, or of a white child of black parents.

Leucophane (lū"ko*fān) noun [ Greek leykofanh`s appearing bright or white; leyko`s white + fai`nein to show: confer German leukophan .] (Min.) A mineral of a greenish yellow color; it is a silicate of glucina, lime, and soda with fluorine. Called also leucophanite .

Leucophlegmacy (lū`ko*flĕg"mȧ*sȳ) noun [ Greek leykoflegmati`a ; leyko`s white + fle`gma phlegm: confer French leucophlegmasie .] (Medicine) A dropsical habit of body, or the commencement of anasarca; paleness, with viscid juices and cold sweats.

Leucophlegmatic (-flĕg*măt"ĭk) adjective [ Confer French leucophlegmatique , Greek leykofle`gmatos .] Having a dropsical habit of body, with a white bloated skin.

Leucophyll (lū"ko*fĭl) noun [ Leuco- + Greek fy`llon a leaf.] (Chemistry) A colorless substance isomeric with chlorophyll, contained in parts of plants capable of becoming green. Watts.

Leucophyllous (lu*kŏf"ĭl*lŭs or lū`ko*fĭl"lŭs) adjective [ Greek leyko`fyllos ; leyko`s white + fy`llon a leaf.] (Botany) Having white or silvery foliage.

Leucoplast (lū"ko*plăst), Leu`co*plas"tid (-plăs"tĭd) noun [ Leuco- + Greek pla`ssein to mold.] (Botany) One of certain very minute whitish or colorless granules occurring in the protoplasm of plants and supposed to be the nuclei around which starch granules will form.

Leucopyrite (lu*kŏp"ĭ*rīt) noun [ Leuco- + pyrites .] (Min.) A mineral of a color between white and steel-gray, with a metallic luster, and consisting chiefly of arsenic and iron.

Leucorrhœa (lū`kŏr*rē"ȧ) noun [ Leuco- + Greek "rei^n to flow.] (Medicine) A discharge of a white, yellowish, or greenish, viscid mucus, resulting from inflammation or irritation of the membrane lining the genital organs of the female; the whites. Dunglison.

Leucoryx (lū"ko*rĭks) noun [ New Latin , from Greek leyko`s + 'o`ryx a kind of gazelle.] (Zoology) A large antelope of North Africa ( Oryx leucoryx ), allied to the gemsbok.

Leucoscope (lū"ko*skōp) noun [ Leuco- + -scope .] (Physics) An instrument, devised by Professor Helmholtz, for testing the color perception of the eye, or for comparing different lights, as to their constituent colors or their relative whiteness.

Leucosoid (-soid) adjective [ New Latin Leucosia , the typical genus (fr. Greek leyko`s white) + -oid .] (Zoology) Like or pertaining to the Leucosoidea , a tribe of marine crabs including the box crab or Calappa .

Leucosphere (-sfēr) noun [ Leuco- + sphere .] (Astron.) The inner corona. [ R.]

Leucoturic (lū`ko*tū"rĭk) adjective [ Leuco- + allan t oic + uric .] (Chemistry) Pertaining to, or designating, a nitrogenous organic substance of the uric acid group, called leucoturic acid or oxalantin . See Oxalantin .

Leucous (lū"kŭs) adjective [ Greek leyko`s .] White; -- applied to albinos, from the whiteness of their skin and hair.

Leucoxene (lu*kŏks"ēn) noun [ Leuco- + Greek xe`nos stranger.] (Min.) A nearly opaque white mineral, in part identical with titanite, observed in some igneous rocks as the result of the alteration of titanic iron.

Leuke (lūk) adjective , Leuke"ness noun See Luke , etc.

Leukæmia (lu*kē"mĭ*ȧ) noun Leucocythæmia.