also: ghost · fake motion · sham motion
Motion out and back that never had anything behind it. The player is not going anywhere and was never going to; the movement itself is the whole point.
A player moves out and comes back without ever being a threat to receive the ball. Unlike return motion, where the returning player may still be part of the play, ghost motion is purely a picture: it exists to make the defense declare, or to move one defender a step, or to look identical to a play where the motion man does get the ball.
The value is entirely in what it costs, which is nothing. An offense gets a coverage read and a defensive adjustment for the price of one player jogging. It can be attached to plays that were going to be run anyway.
ghost, sham motionreturn motion, jet motion and jet sweepGhost is used loosely for several things, including a route concept where a player fakes a route he does not run. The motion sense is the one meant here, and hearing the word does not by itself tell you which.