• (a.) Having one hydrogen atom replaceable by a negative or acid atom or radical; capable of neutralizing a monobasic acid; -- said of bases, and of certain metals.
Mon·ac'id adjective [ Mon- + acid .] (Chemistry) Having one hydrogen atom replaceable by a negative or acid atom or radical; capable of neutralizing a monobasic acid; -- said of bases, and of certain metals. 
monacid Having the power of saturating one molecule of a monobasic acid.