expression, ichidan verb
be outwitted; be taken in; be forestalled
Passive of してやる (to do something for someone, or to outwit someone). Used when one is outsmarted, tricked, or beaten to the punch by another person. Often carries a nuance of being one-upped or having the tables turned.
See also: して遣る
まさか彼にしてやられるとは思わなかった。
I never thought I'd be outwitted by him.
先を越されて、完全にしてやられた。
They beat me to it, and I was completely taken in.