Interesting... all the places I've seen the word, it meant a winged unicorn*. But reading this post drove me to look it up, and I did find both definitions. Less Wrong: raising new interest in definitions of mythological creature parts! :)

*Speaking of mythological definitions, I learned somewhere to distinguish between an alicorn, which has the goat-like body, lion's tail, beard, etc. of a unicorn, vs a horned pegasus, which has horse-like features. Not sure where that came from, but it's firmly implanted in my stores of useless knowledge.