1) When you take your finger and run it around a guy's asshole while you jerk the guy off into his own shit.
2) When you 69 and fill each other's mouths with cum; then you turn over and blow splooge into each other's assholes.
3) When you take a scuba snorkel and put your cock in the wee bendy mouth part, then sneak the other end right up your back address. Then you grab the middle of the snorkel and you're fuckin' your own ass and runnin' your own crank until you're standin' in a pile of your own jizzum.
3) When you fist a guy and then open up your hand inside his asshole and grab whatever you can. Whatever you come out with, you rub on his dick.
4) Could be a straight move. When you take a girl out for a huge dinner, but don't let her go to the can. Then you have anal sex and she shits all over your dick; when you're about to come you pull out and blow shit all over her tits. That's the Rusty part; the Venture part is when you eat it without using your hands.
5) When you jerk off so much your dick gets all red and sore.
The Rusty Venture is a mysterious maneuver from the Castro community of the 1970s.