The act of ejaculating in your partner's ass and then using a piece of plastic tubing to suck the semen back out (or have your partner do so, if long enough), similar to how gas was syphoned out of cars during the oil crisis of the early 1970s.
My freaky girlfriend loves the taste of cum and shit so I convinced her to let me give her a 1970s gas crisis.
1970's Gas Crisis is the term for a sex act in which a length of plastic tube is inserted into the partner's anus, and sucked on. The act is so named because it appears similar to the gas siphoning that occurred during the gas crisis in the 1970's, where people would suck on a pipe to start the flow of fuel from one source to another.
My ass really hurts after last night, but my partner really wanted to experience the 1970's Gas Crisis.