1) Apace 
at full gallop; headlong
• (adv.) Swiftly; speedily; rapidly; -- a fox-hunting term; as, to ride tantivy. • (n.) A rapid, violent gallop; an impetuous rush. • (v. i.) To go away in haste.
Tan·tiv'y adverb [ Said to be from the note of a hunting horn.] Swiftly; speedily; rapidly; -- a fox-hunting term; as, to ride tantivy . Tan·tiv'y intransitive verb To go away in haste. [ Colloq.] Tan·tiv'y noun A rapid, violent gallop; an impetuous rush. Cleverland. 
HMS Tantivy was a British T Class patrol type submarine of 1090 tons displacement launched in 1943. HMS Tantivy had a top speed of 15.25 knots surfaced and 9 knots submerged, carried a complement of 53 and was armed with one 4 inch dual-purpose gun; one 20 mm anti-aircraft gun; three machine-guns and about ten 21 inch torpedo tubes.