A metrical foot consisting of three long syllables.
2A Molossian dog.
Late 16th century; earliest use found in William Webbe (fl. ?1566–1591), author. From classical Latin Molossus (also Molossos) metrical foot consisting of three long syllables, a Molossian dog, also as adjective, from ancient Greek Μολοσσός, adjective, also in Hellenistic Greek as noun in sense 1.