A "bieber" is a dick that is so small that the foreskin is actually longer than the penis - meaning it looks like an inside out condom stuck on your girlfriend's clit. In order to bang a guy with a "bieber", a chick would have to stick the end of a straw down her snatch and stick the other end under the dude's foreskin into his dickhole, while he masturbates himself up the ass with a dildo until he gets off (seeing as he has no shaft). Circumsized males with beebers end up looking like they have a 3 year old girl's vagina. This deformity was named after Justine Bieber, a noted transexual pop singer who became infamous after she leaked a sex tape of Usher playing with her "bieber".
Melissa agreed to have sex with Roger after the junior prom until he dropped his pants and she saw he had a bieber. After she told all his friends, Roger went home and slit his wrists until he bleed to death.