Abbreviation for "Oh my God" or "Oh my gosh". Often used by teenage girls while texting, and using any other sort of online chatting. Used so often it has now become redundant.
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 1: i just bought new shoes
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