Mythical horse (7)
(Other definitions for pegasus that I've seen before include "Immortal winged horse of Greek mythology" , "Constellation in the northern hemisphere near Andromeda and Pisces" , "Flier" , "Winged horse of Greek myth" , "mount in the clouds" .)
(Other definitions for unicorn that I've seen before include "wonder horse" , "Fabulous horned animal" , "Imaginary one-horned creature" , "Heraldic creature" , "that's fabulous" .)