Though commonly used to describe a member of the opposite sex, "tease" can also apply to members of the same sex, in the case of homosexuality or weekly drunken bisexuality.
A tease is
(A) someone who either offers to engage in affectionate behavior with you, such as making out, and then denies you the privilege of doing so, or
(B) someone who only gives you a small fraction of what you actually want from them, such as a kiss when you are dying to make out with them. A tease may even go so far as to kick you out of the room, and in extreme cases, he or she will then proceed to have affectionate relations with someone else, torturing you even more. Other scenarios may also include promising--and subsequently denying to provide--a raincheck.
It is vital that this definition be used as the one and only definition of a tease, as looking the word up in dictionaries and on Google will often provide a two-word answer: Paige Duckworth.
Paige, you're such a tease.