1. American slang: A person who is hot, i.e. sexually desirable. The term can be applied to both men and women, and used by both homosexual and hetereosexual speakers. Usage dates back to the early 1990's, according to the Random House Historical Dictionary of American Slang.
"This hottie got a body and I wanna get naughty" -- Sir Mix-a-Lot ("Sprung on the Cat," 1992).
2. British slang (Also Australia and New Zealand): A hot water bottle.

Additional Sources:
Patrick Atoon, et. al. The Rap Dictionary. <http://www.rapdict.org/terms/h> (24 September 2003)
Donna Richoux. "Re: babe[WAS: Photo Gallery]," 17 January 2001, <alt.usage.english> (24 September 2003) .
"Hottie." The Phurba Etymologicon. <http://www.panikon.com/phurba/alteng/h.html> (24 September 2003)
Oxford English Dictionary.