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.