A person who Acts/Looks like Justin Bieber,
or attempts to disguise themselves as Justin Bieber.
This sometimes happens with teenage boys who think that if they act/look like Justin Bieber then they have a chance at getting laid.

Someone who looks, acts, sings, or dances like Justin Bieber. This includes, but is not limited to, a new Bieber-like haircut, random chick-like dancing, or obsessive squeaky-voiced singing.

Teenage guys who try desperately to look like Justin Bieber. Bieber wanna-be's; wanna-biebers.

A pathetic teenage boy who imitates Justin Bieber in the hope that they will be more likely to get girls. Usually has swishy hair and sings Justin songs to himself.

Someone who greatly resembles Justin Beiber.

Ie: Hairstyle, Clothing, etc.