- Occurring every fourth day, counting inclusively, or every 72 hours. Used of a fever.
- A malarial fever recurring every 72 hours.
- Having to do with the fourth; especially, occurring every fourth day: as, a <em>quartan</em> ague or fever (one which recurs on the fourth day—that is, after three days).
- An intermitting ague that occurs every fourth day, both days of consecutive occurrence being counted, as on Sunday, Wednesday, Saturday, Tuesday, etc.
- A measure containing the fourth part of some other measure.
- Of or pertaining to the fourth; occurring every fourth day, reckoning inclusively.
- An intermittent fever which returns every fourth day, reckoning inclusively, that is, one in which the interval between paroxysms is two days.
- A measure, the fourth part of some other measure.
- A <xref>fever</xref> whose symptoms recur every four days.
- Recurring every four days; especially in designating a form of <xref>malaria</xref> with such symptoms.
- a malarial fever that recurs every fourth day
- occurring every fourth day (especially the fever and weakness of malaria)