What does ohmygod mean?

Oh, my God, it means my God. It usually means unexpected and can be used to surprise and intimidate different situations.

Example:

My god, the room is so dirty.

God, the room is so messy.

Oh, my God! Oh, my god. I was admitted to Yale University!

Oh, my God! I was admitted to Yale University.

Derivative drama:

"Oh, my God" is a mini-drama of "Moon Fire" broadcast by Korean KBS TV1October 20151KLOC-0/6. Starring Shin Min A and Ji-seob So. The play is a romantic comedy, which tells the story that the hero and heroine get married when they are young, meet again when they are adults and lose weight together, and at the same time have new ideas about health and love.