Dirt Biking is the act of having sex with a woman on all fours. While in the act, the male slips his thumb into her anus and then makes motorcyle sounds while pumping the "throttle". The time that elapses from insertion of thumb until the time you get thrown off is to be compared amung buddies.

v. collectively or individually finding someone/something to blame for a problem, as opposed to brainstorming which connotes finding solutions to a problem

n. the act of finding someone/something to blame for a problem

(from a TV ad for HD television)

When someone has terrible diarrhea and sprays shit up the back the toilet bowl/tank.