The Joker as used in sexual reference:

The act of removing a tampon at the string by mouth from a womans vagina while on her period. Once removed, the bloody tampon is swung back and forth by the string "while still in the teeth" as if shaking your head "no."

The blood like smile/outline from ear to ear that is left behind is know as "The Joker."
(Similar to the make-up smile on the Joker)

A very sick sexual act. Why some find this stimulating i'll never know.
When the woman is having her menstrual peiod, the man gives oral sex and wipes his face sideways across the vagina several times. Having a blood-stained "smile" on his face he looks up to her and says "Why so serious?".

You give a girl The Joker when you have sex with her while she is on her period, you take your bloody dick, and draw smile lines on her face.

While having sex, the woman says in her most cum hungry voice "go on my face". As his eyes close in euphoria and he busts his nut, she cups it in her hands. As soon as he opens his eyes, she chucks it all over his mouth (to resemble jokers scars) and starts laughing hysterically. When he looks at her all confused and angry, she says "why so serious?", then walks away.
(can also be used for men, but intended for women).

someone that is or does something stupid. a mild insult.

When you go to the bathroom for a dump and know right away its gonna be a good one and you'll feel satisfied after. Very similar to when a hitter in baseball hits a long home run aka a no doubter

A very attractive psycopath appearing in the movie "The Dark Knight". Also a less hot psycho appearing in many other movies.