"A tease" is a person who plays with other people's desires. They offer something that you want, but then don't give it to you.
For example, "a tease" very often describes a woman who acts like she's attracted to a man, but then won't go out with him or sleep with him.
Despite its meaning, the word "tease" doesn't really sound very negative. It sounds kind of fun and playful. You can even say this to a child who offers you something but then takes it back:
A: Do you want this red crayon?
A: No, you can't have it.
B: Oh, you're such a tease!