Can also be substituted as "omigosh", "omigod", or "omigawd".
Can become highly annoying when said a lot, along with other words such as "like", "totally", "lolz" in a chatroom.
Girl 2: omg!!! are they hot?
Girl 1: like, totally!!!!
Girl 1: omg did u c that guy over there? hes like, so hot!
Girl 2: tottttally
Girl 3: no hes not! hes ugly! lolz omg i cant believe u guys thought he was hot
Correct Response - "Speak proper, or STFU, N00B!"
Silent then proceeds to sock her in the face.
Simply put OMG means, Oh my god!
Person 2: "O M G. , have they even heard of the word fashion."