Lipstick Lesbian
A lipstick lesbian is a woman who is putting up a front of being a lesbian when in fact, she is merely curious about lesbianism.

The use of the word lipstick refers to the fact that these women are putting up a sexual facade similar to the facade that women of all sexual orientations put on when they apply make-up. Make-up hides the real woman underneath, and a woman who is a lipstick lesbian is also similarly putting on a front. While being with a woman is something they have desired, they ultimately are just curious and not serious.
Lesbian1: That girl has been flirting with me all night! I'm going to make my move.

Lesbian2: Don't bother. I tried for the last month and she won't do anything except kiss. She's just a lipstick lesbian.