It is portmanteau of Justin Bieber and Comment. It refers to the remarkable funny top comment made on Justin bieber on websites, blogs, jokes, news etc.

Etymology of the word says that this became famous when people visited any news, video, blog etc. about Justin Bieber just Only to SEE the funny comments.
Baby ft. Ludacris Top Comments :

"penis and glue for justin beaver...paste glue here and on ur pussy and then enjoy "

Second Top Comment (Bieberment):

"i came here for bieberment"
by mark.robins210 April 27, 2012
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The Bieber: The insertion of a bottle of cheap beer into the rectum of a male by another male in a game of twister on the 3rd wednesday of May in honor of Justin Bieber.
"Dude, it's almost that time of the year again. Me and some homies are gonna go do the Bieber at my house after work."
by ArtCheerio February 17, 2014
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A very small penis, around 3 inches or less in length and circumference, like Justin Biebers penis.
Girl: "I was gonna give my new boyfriend a blowjob last night, but pulled down his pants and saw that he had a Bieber. I laughed and broke up with him immediately."
by bieberhasnoballs May 24, 2010
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To use part of Justin Bieber's name mixed with a word or phrase.
Bieberism

Whats up Biebizzl.
Your such a lazy Bieber.
by iluvhils April 19, 2010
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To use the name of a Justin Bieber song in a normal conversation.
In my world I am one less lonely girl. (These are Bieberisms)
by Sophie Michelle April 4, 2010
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Like a weiner only smaller.

A very small penis.

Named in honour of popular singer Justin Bieber, a small weiner believed by many to have an extremely small penis.
Q: I heard Justin Bieber's weiner is just a bieber. Can that be true?

A: Yes indeed: modern science has shown it to be negligibly small.
by Pipe Downn November 13, 2010
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A unit of measurement used to gauge the level of discomfort caused by hemorroids. Each unit is roughly equivalent to the pain and discomfort of watching a Justin Bieber video.
by Darwin Bonaparte June 1, 2010
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