When a woman, on her knees, jerks off two guys that are facing each other at the same time, one with each hand. The two guys are standing, facing towards each other, with her kneeling between them. The woman jerks off both guys simultaneously by moving both of her hands left, and then right, in unison. She continues this motion in rapid succession until taking a double shot of man seed to the face. The act gets its name from the similarity that her hand motions have to those of a kid riding a BMX bike and throwing the handlebars left and right as he tries to pedal faster. Can’t picture it? Get on your knees and try it!
Bob: Hey, don't you know that chick?
Tom: Yeah, she was BMXing me and my roommate the other night. Nice girl.