Definition of tertian

< tertial

tertiary >

ter·tian    (tûrshn) KEY 

ADJECTIVE:

Recurring every other day or, when considered inclusively, every third day: a tertian fever.

NOUN:
Pathology

A tertian fever, such as vivax malaria.

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ETYMOLOGY:
Middle English terciane, tertian fever, from Latin (febris) tertina, (fever) of the third (day), from tertius, third; see trei- in Indo-European roots