1 Greek Mythology The son of Zeus and Danae, a hero celebrated for many achievements. Riding the winged horse Pegasus, he cut off the head of the Gorgon Medusa and gave it to Athena; he also rescued and married Andromeda, and became king of Tiryns in Greece.
2 Astronomy A large northern constellation that includes a dense part of the Milky Way. It contains several star clusters and the variable star Algol.
2.1 (as genitive Persei /ˈpərsēˌī/) Used with a preceding letter or numeral to designate a star in this constellation:the star Delta Persei