E·phēm'e·rā, n.

n. [N. Lat. (sc. febris), Gr. πυρετός ἐφήμερος, from ἐφήμερος, daily, and lasting but a day, from ἐπί and ἡμέρα, day.] 1. (Med.) A fever of one day's continuance only. 2. (Entom.) The day-fly, or May-fly, a genus of insects; strictly, a fly that lives one day only; but the word is applied also to insects that are very short-lived; —called also ephemeron.