an exclamation that can be used in many circumstances. it is a less profane version of "oh my fuckin god" and more positive. it can be used when something is funny, surprising, or maybe dumb.
Peppa: George, we won the lottery!
George: OH MY HECKIN' GOD
George: oops i've spilt your tea
Peppa: ugh oh my heckin god ur cancelled
Peppa: OH MY HECKIN GOD ! GEORGE LOOK AT THIS MEME i'm laughing so hard
George: HAHAHA OH MY HECKIN GOD
Mean that something, whatever it is, is very extreme.. and girls tend to say it way too much in those high school movies..
Jessi: "Hey Amy, did you hear that mike stabbed James and turned to hulk then smashed his head and ate his insides and scratched his face?"
Amy: "Oh.. really?"
Jessi: "Yeah you should've seen his face it was SO UGLY, like, oh my god!!!!"
what little rage kids say when someone kills them on forknife
oh my god your so trashhh go home to you mam