Quintan \Quin"tan\, a. [L. quintanus, fr. quintus fifth, quinque
five. See {Five}.]
Occurring as the fifth, after four others also, occurring
every fifth day, reckoning inclusively; as, a quintan fever.
-- n. (Med.) An intermittent fever which returns every fifth
day, reckoning inclusively, or in which the intermission
lasts three days.
[1913 Webster]