Qua*ter"na*ry (?), a. [L. quaternarius consisting of four each, containing four, fr. quaterni four each, fr. quattuor four: cf. F. quaternaire. See Four.]

1. Consisting of four; by fours, or in sets of four.

2. (Geol.) Later than, or subsequent to, the Tertiary; Post-tertiary; as, the Quaternary age, or Age of man.

Qua*ter"na*ry, n. [L. numerus quaternarius: cf. F. quaternaire.] 1. The number four. Boyle.

2. (Geol.) The Quaternary age, era, or formation. See the Chart of Geology.

• of fourth rank or order
  
• of a mathematical expression containing e.g. x4
  
• a geological period