The Collaborative International Dictionary of English v.0.48:

monacid \mon*ac"id\, a. [Mon- + acid.] (Chem.)
   Having one hydrogen atom replaceable by an acidic atom or
   radical.

   Syn: monoacid, monoacidic, monacidic.
        [1913 Webster]

   2. Capable of neutralizing one equivalent of a monobasic
      acid; -- said of bases, and of certain metals.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

monacid \mon*ac"id\, n. (Chem.)
   An acid having one replaceable hydrogen atom.

   Syn: monoacid.
        [PJC]