Pronunciation: (u-rī'un),[key] —n., —gen.Or•i•o•nisPronunciation: (ôr"ē-ō'nis, or"-, u-rī'u-nis)[key]for 2. 1. Class. Myth.a giant hunter who pursued the Pleiades, was eventually slain by Artemis, and was then placed in the sky as a constellation.
2. Astron.the Hunter, a constellation lying on the celestial equator between Canis Major and Taurus, containing the bright stars Betelgeuse and Rigel.
3. Mil.a land-based U.S. Navy patrol plane with four turboprop engines, used to detect, track, and destroy enemy submarines and armed with missiles, torpedoes, mines, and depth bombs.