What is omgOMG?

OMGOMG is a way, mostly used by girls on social media, to tell someone how enthousiastic you are (or to show that there's something going on).

Person 1: *texts* OMGOMG OMGOMG OMGOMG OMGOMG
Person 2: *texts* WHAT
Person 1: *texts* IM HUNGRY
Person 2: *texts* OMG CALL 911

omgOMG - meme gif