(kwə·tûr′nə·rē) adjective
1. Consisting of four things.
2. Fourth in order.
—noun plural ·ries
1. The number four; a group of four things.
2. Math. A quantic function having four variables. [<L quaternarius <quaterni by fours]

(kwə·tûr′nə·rē) adjective Geol.
Of, pertaining to, or designating a geological period and system of the Cenozoic era, following the Tertiary and still continuing.
—noun The Quaternary system or period.