1. [ noun ] (geology) last 2 million years
Synonyms: Age_of_Man Quaternary_period
Related terms: period Cenozoic Pleistocene Holocene
2. [ adjective ] (geology) coming next after the third and just before the fifth in position or time or degree or magnitude
Synonyms: fourth 4th

"the quaternary period of geologic time extends from the end of the tertiary period to the present"

Related terms: ordinal
3. [ adjective ] consisting of or especially arranged in sets of four
Synonyms: quaternate

"quaternate leaves" "a quaternary compound"

Related terms: multiple
4. [ noun ] (mathematics) the cardinal number that is the sum of three and one
Synonyms: four 4 quartet quatern tetrad quaternity quaternion quadruplet foursome Little_Joe IV
Related terms: digit
Similar spelling:   quatern