Is is a mispronunciation of the word "pro" to emphasise how pro a person/thing is. It is often used in gaming communities and can also indicate sarcasm.
That kill was crazy pruh
ur just 22 pruh
Bourrelets trop géniaux
OMG nn mé allo koi la meuf elle avais pa de pruh
elle a trop du pruh c grv bi1