a. A fabled creature symbolic of virginity and usually represented as a horse with a single straight spiral 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 spiral 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.
a. Something that is greatly desired but difficult or impossible to find: “Is antigravity the unicorn of physics? Or do we simply lack the strategy and bait to catch it in an experimental snare?” (Jerome Groopman).
b. Business A startup company valued at one billion dollars or more.
[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
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.