recurring on the seventh day (i.e., six days after the previous episode).
Denoting a malarial fever the paroxysms of which recur every seventh day, counting the day of the occurrence as the first day (that is, with a 5-day asymptomatic interval).
[L. septem, seven]
septan(sĕp′tăn) [L. septem, seven]
Recurring every seventh day.