a. A fabled creature symbolic of virginity and usually represented as a horse with a single straight spiraled horn projecting from its forehead.
b. Heraldry A representation of this beast, having a horse's body, a stag's legs, a lion's tail, and a straight spiraled horn growing from its forehead, especially employed as a supporter for the Royal Arms of Great Britain or of Scotland.
2. Unicorn The constellation Monoceros.
[Middle English unicorne, from Old French, from Late Latin ūnicornis, from Latin, having one horn : ūnus, one; see oi-no- in the Appendix of Indo-European roots + cornū, horn; see ker-1 in the Appendix of Indo-European roots.]
(click for a larger image)unicorn
The Lady and the Unicorn: "Sight,"one in a series of six 15th-century tapestries
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