What is a northen constellation near the vernal equinoctial point. Its three brightest stars, with the brightest star of Andromeda, form the square of Pegasus called?

pegasus — (Astron.) A northen constellation near the vernal equinoctial point. Its three brightest stars, with the brightest star of Andromeda, form the square of Pegasus. (Webster's 1913.)

Sources