Pertaining to or resembling a lion; lion-like: as, leonine fierceness or rapacity.In prosody, consisting of metrical Latin hexameters or elegiacs (alternate hexameters and pentameters), in which the final word rimes with the word immediately preceding the cesural pause or the middle of the line.Pertaining to a person named Leo, particularly to several popes of that name; more specifically, of or pertaining to Leo I., the Great (pope from 440 to 461), who is said to have added certain words to the Roman canon of the mass, and whom some have even, without good reason, described as the author of the Roman liturgy.n. A coin illegally imported into England by foreign merchants in the reign of Edward I.n. plural Leonine verse.