Lewis & Short

3. Mĕgăreus (trisyl.), i, m., = Μεγαρεύς, a son of Neptune, and father of Hippomenes, Hyg. Fab. 157 and 185; Ov. M. 10, 605.
Hence, Mĕgărēĭus, a, um, adj., of or belonging to Megareus, Megareian (poet.): heros, i. e. Hippomenes, Ov. M. 10, 659.