Dictionary definition · Quaternary
noun
- the period of the last 2 million years
- the cardinal number that is the sum of three and one
adjective
- consisting of or especially arranged in sets of four"quaternate leaves"
- 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"
Source: Open English WordNet (CC BY 4.0).