quaternary Definition

quaternary
adj

1. Having or consisting of four parts.
2. Fourth in a series.
3. geol.
Belonging or relating to the most recent period of geological time when humans evolved.
Form: Quaternary
4a. chem.
Said of a compound, especially one containing nitrogen: having the central atom bound to four other atoms or groups;
4b. chem.
Said of an atom: bound to four other atoms or groups.

noun

1. geol.
The Quartenary period or rock system.

Etymology: 15c: from Latin quaterni four each.