Of or pertaining to the fourth; occurring every fourth day, reckoning inclusively; as, a quartan ague, or fever. [1913 Webster]
, n.
An intermittent fever which returns every fourth day, reckoning inclusively, that is, one in which the interval between paroxysms is two days. [1913 Webster]
A measure, the fourth part of some other measure. [1913 Webster]