It means "you betrayed me" or "you deceived me". Good luck!

You cheated me. يغدر means be disloyal. غدر treachery.

it means... you cheated on me

Hi Mah, beside the meanings of غدر , which was given by the friends above, I think there is a mistake. The verb غدر needs usually the preposition بــــ . So maybe you mean غدرت بي which means "she betrayed me" , or عذرتني which means "she forgave me , or غادرتني which means "she left me"