A sex act. Has a variety of definitions depending on your region in the States, but it's generally associated with male homosexual sex. The term originated in the 80s, possibly started by "Horace Gentlemen" out of Provincetown, Massachusetts. Whenever The Rusty Venture is brought up in conversation, they almost always argue about what exactly it is.
Depending on who you ask and in what region of the States, a Rusty Venture is:
1) taking your finger and running it around a guy's asshole while you jerk the guy off and he's uncircumcised
2) where two men 69 and they fill each others mouths with seamen, then turn over and blow splooge into each other's assholes (not to be confused with a Snake Venom)
3) where you take a SCUBA snorkel and put your dick in the mouthpiece, then snake the other end up into your ass, then jerk off until you manage to ejaculate into your own ass (not to be confused with a Double Frogman)
4) when you jerk a guy off, clench his semen in your fist, shove your hand into his ass, open your fist, and whatever you come out with, rub it on his ass cheeks
5) conversely, a straight sex position that involves a "Rusty" part and a "Venture part. The Rusty part is where a man takes a girl out for a huge dinner, but then not let her go to the bathroom. Then he has anal sex with her, she she shits on his dick. He pulls out and ejaculates on her back. The "Venture" part is where he eats that mess off her back without using his hands.
6) when two people fill a tub with questionable content (syrup, shit, etc), have lots of sex in said tub, then eat the content of the tub with turkey basters
7) a handjob in which the dick in question is covered in shit
8) when a man masturbates so much that his dick gets all red and sore