An extremely well thought out sex act that requires advance planning. You begin by dropping a medium to large sized deuce in the toilet. Take said deuce out of the toilet, wrap it in saran wrap and put it in the freezer for 6 hours. After the deuce is thoroughly frozen, take it out and give it to your girlfriend. She then takes the deuce and proceeds to masturbate with it. As the deuce thaws, it slowly deteriorates and clogs up her pussy... hence the log jamming action.
Damian1381 convinced his girlfriend to take part in a Louisiana Log Jammer session with him. Three days later, she came down with a yeast infection.