A birelfucker is simply defined as somebody who partakes in sexual intercourse with one or more birel racing karts on a regular basis, usually via the furthermost rear section of the chassis with the rear bumper assembly removed to facilitate access to the inner frame rails (with sizes ranging from 28-32mm internal diameter) for the purpose of sexual intercourse, usually to orgasm. This is often done with any available lubricant on hand such as premix oil. Although the term "birelfucker" is relatively new, it is highly offensive to kart racers and non-kart racers alike.
"That guy is such a birelfucker! In fact, he in the definition of birelfucker! He practically invented birelfucking!"
by The softest of all the tacos March 22, 2007