When you see a lady with her large hands hanging out of a window of a car, and she is waving them about the air.
It is also a large, stiff penis.

Referring to women who are sexually or romantically attracted to other women. Applies to both lesbians and bisexual women, as it is only the same-sex attraction that matters, not any other attractions the women may have.

Originates from the Greek poet Sappho, a bisexual woman from the Isle of Lesbos, from which we get the term lesbian.