Definition of Pegasus
1 Greek Mythology a winged horse that sprang from the blood of Medusa when Perseus cut off her head.
2 Astronomy a large northern constellation, said to represent a winged horse. The three brightest stars, together with one star of Andromeda, form the prominent Square of Pegasus. (as genitive
Pegasi /ˈpegəsī/)
used with a preceding letter or numeral to designate a star in this constellation:the star Zeta Pegasi