Quar"tan (?), a. [F. quartain, in fièvre quartaine, L. quartanus, fr. quartus the fourth. See Quart.] Of or pertaining to the fourth; occurring every fourth day, reckoning inclusively; as, a quartan ague, or fever.

Quar"tan, n. 1. (Med.) An intermittent fever which returns every fourth day, reckoning inclusively, that is, one in which the interval between paroxysms is two days.

2. A measure, the fourth part of some other measure.