Tertian \Ter"tian\, a. [L. tertianus, from tertius the third. See Tierce.]

(Med.) Occurring every third day; as, a tertian fever.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Tertian \Ter"tian\, n. [L. tertiana (sc. febris): cf. OF. tertiane.]

1. (Med.) A disease, especially an intermittent fever, which returns every third day, reckoning inclusively, or in which the intermission lasts one day.

2. A liquid measure formerly used for wine, equal to seventy imperial, or eighty-four wine, gallons, being one third of a tun.

Source: Webster's Revised Unabridged Dictionary (1913)