[qua.ter.na.ry] adj [L quaternarius, fr. quaterni four each] (1605) 1 a: of, relating to, or consisting of four units or members b: of, relating to, or being a number system with a base of four
2. cap: of, relating to, or being the geological period from the end of the Tertiary to the present time or the corresponding system of rocks--see geologic time table
3: consisting of, containing, or being an atom bonded to four other atoms
[2]quaternary n, pl -ries (1880) 1 cap: the Quaternary period or system of rocks
2: a member of a group fourth in order or rank