The act of which requires two men, a tube, and a trained gerbil. Basically a combo of felching and gerbiling. One man ejaculates into the rear end of one man while the other does the same to guy #1. Then a tube is inserted into the anus of both men, and a gerbil goes into one of their buttholes, sucks the cum out of their butthole, crawls to the other man's butthole and places his own sperm into his butthole, the action is repeated.
"Yeah me and my boyfriend tried gwelching the other day."
"How was it?"
"Kind of itchy."