A word used to aggravate people over the internet. It is used as a joke to signal you want to fight them. No one takes it seriously, and if they do it is because they are a squeaker.
squeaker: hey m9 fite me irl
MLG pro: nah m8 im 2 mlg 4 u, i hit a 1080 triple pistol switch quickscope noscope window shot while getting a triple positive k/d. il rek u