Sentence:  "Rarity:" Why, you've become an <WSD>alicorn</WSD>! I didn't even know that was possible.<br />"Pinkie Pie:" "[wearing a costume horn and wings]" <WSD>Alicorn</WSD> party! 
Meaning of the word marked with <WSD> tags:  A mythological creature, a mixture of pegasus and unicorn: a winged horse with a single horn on its head.