\Quar"tan\, a. [F. quartain, in fi[`e]vre 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.