Leo \Le"o\ (l[=e]"[=o]), n. [L. See {Lion}.] (Astron.) 1. The Lion, the fifth sign of the zodiac, marked thus [[Leo]] in almanacs. 2. A northern constellation east of Cancer, containing the bright star Regulus at the end of the handle of the Sickle. {Leo Minor}, a small constellation between Leo and the Great Bear.