quaternary: Meaning and Definition of

quat•er•nar•y

1. consisting of four.
2. arranged in fours.
3. (cap.)noting or pertaining to the present period of earth history, forming the latter part of the Cenozoic Era, originating about 2 million years ago and including the Recent and Pleistocene Epochs. See table under
4. (of an alloy) having four principal constituents.

1. a group of four.
2. the number four.
3. (cap.)the Quaternary Period or System.