Grinding movement, sometimes with only minimal clothing on. Can be anything from making out up to sex (but usually not including). More common in chicago/midwest.
intentionally bleeding, in professional wrestling.
In pro wrestling, a wrestler will, at times, nick themselves with a hidden razor blade to show blood on camera. This helps sell the intensity of the fight to the audience. Oftentimes, the juicer will take aspirin before the fight to thin his blood, causing even more blood flow on-camera.
"Did you see how badly Ric Flair was bleeding last night?"
"He was juicing, huh?"
"Guy should call himself 'Tropicana'."
The involuntary release of semen and possibly some combination of feces and blood into undergarments from the vagina or anus via a queef or fart. Almost always an extremely worn out and loose orafice is partly to blame for the juicing. The individual who has juiced themselves is left to deal with a sticky, sloppy, smelly mess and is probably a whore for letting someone give them a creampie or mudpie.
Q: What the fuck is that smell?
A: Aw, shit that bitch is juicing herself!
or
Q: Mommy, where are there so many pinkish, crusty stains on your panties?