Source : Webster's Revised Unabridged Dictionary (1913)

Quaternary \Qua*ter"na*ry\, a. [L. quaternarius consisting of
   four each, containing four, fr. quaterni four each, fr.
   quattuor four: cf. F. quaternaire. See {Four}.]
   1. Consisting of four; by fours, or in sets of four.

   2. (Geol.) Later than, or subsequent to, the Tertiary;
      Post-tertiary; as, the Quaternary age, or Age of man.

Quaternary \Qua*ter"na*ry\, n. [L. numerus quaternarius: cf. F.
   quaternaire.]
   1. The number four. --Boyle.

   2. (Geol.) The Quaternary age, era, or formation. See the
      Chart of {Geology}.

Source : WordNet®

Quaternary
     n 1: last 2 million years [syn: {Quaternary period}, {Age of Man}]
     2: the cardinal number that is the sum of three and one [syn: {four},
         {4}, {IV}, {tetrad}, {quatern}, {quaternion}, {quaternity},
         {quartet}, {quadruplet}, {foursome}, {Little Joe}]