When u see someone/something thats hella embarrasing like wtf Or when someone cheer u up/joking at u. Issa acronym from u r so fucking annoying:)
Hellen : Bitch u look like gigi hadid today!
Zelin : USFA!
Jmt issa slang of just my thought.
U use it when u r in an argument or you give your friend an advice or fuck you really want me to describe it with a long ass paragraph?
He obviously doesnt like you, jmt sarah.