definition of
quaternary

[1] #1 quaternary n. [Quaternary, Quaternary period, Age of Man] last 2 million years. wn

[2] #2 quaternary s. [quaternate] consisting of or especially arranged in sets of four; "quaternate leaves"; "a quaternary compound". wn

[3] #3 quaternary n. [four, 4, IV, tetrad, quatern, quaternion, quaternity, quartet, quadruplet, foursome, Little Joe] the cardinal number that is the sum of three and one. wn

[4] #4 quaternary s. [fourth, 4th] coming next after the third and just before the fifth in position or time or degree or magnitude; "the quaternary period of geologic time extends from the end of the tertiary period to the present". wn