quaternary
1. qua.ter.na.ry \'kwa:t-*(r)-.ner-e-, kw*-'t*r-n*-re-\ aj [L quaternarius, fr. quaterni four each] 1: of, relating to, or consisting of four units or members : QUADRUPL E cap 2: of, relating to, or being the geological period from the end of the Ter tiary to the present time or the corresponding system of rocks 3: consisting of, containing, or being an atom united by four bonds to car bon atoms 2. quaternary n 1: a member of a group fourth in order or rank cap 2: the Quaternary period or system of rocks
Webster's English Dictionary