manta ray /ˈmæntə ɹeɪ/ noun1 •Any of several very large pelagic rays formerly of the genus Manta, now placed in genus Mobula, with winglike pectoral fins, a long tail, and two fins resembling horns that project from the head.My favorite are the manta rays. We watch them wing past. The have the largest brain of any fish, I remember. — 2020 formsmanta rays