Etymology: (1400–50; late ME < L quaternārius consisting of four =quatern(ī) four at a time +-ārius -ary)
Definition of 'quaternary'
Princeton's WordNet
1. (noun)Quaternary, Quaternary period, Age of Man last 2 millionyears
2. (adj)four, 4, IV, tetrad, quatern, quaternion, quaternary, quaternity, quartet, quadruplet, foursome, Little Joe the cardinalnumber that is the sum of three and one
3. (adj)quaternate, quaternary consisting of or especially arranged in sets of four "quaternate leaves"; "a quaternary compound"
4. (adj)fourth, 4th, quaternary 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"
Definition of 'quaternary'
Webster Dictionary
1. (adj)quaternary consisting of four; by fours, or in sets of four
2. (adj)quaternary later than, or subsequent to, the Tertiary; Post-tertiary; as, the Quaternary age, or Age of man
Definitions of quaternary 
