also: tight end trade · trading the tight end
Moving the tight end from one side of the formation to the other before the snap. A shift rather than a motion. It changes the formation's strength, which is what makes a defense re-declare.
The tight end moves from one side of the formation to the other and sets. He is normally the player who defines formation strength, so trading him flips strength, and a defense that has declared its front and coverage to a side now has them declared to the wrong one.
It is a shift rather than a motion, which matters because he has to be set again before the snap. It is normally done deliberately late for exactly that reason.
tight end trademotion and shift, unbalancedTrade and motion are both pre-snap movement and get lumped together in conversation, but a trade is a shift, and the set-again requirement is what separates them. See the motion and shift entry.