adj. & n.
adj. 1 having four parts. 2 (Quaternary) Geol. of or relating to the most recent period in the Cenozoic era with evidence of many species of present-day plants and animals (cf. PLEISTOCENE, HOLOCENE). °Cf. Appendix II.
n. (pl. -ies) 1 a set of four things. 2 (Quaternary) Geol. the Quaternary period or system.
[ ME f. L quaternarius f. quaterni distrib. of quattuor four ]