What it means....
I think the tern is total and complete JUNK.
But, if you want a definition of the way it is used...well...ok...:
Stuck (Behind You) -
When the club gets below plane on the downstroke, and all the kings horses, and all the kings men, can't "get back on top of it" fast enough to hit it straight.
The ball can go "right-to-right" or if the face closes, left.
To pose it in the true "troubleshooter" tradition of a Rick Smith, from a near top of the back swing position, try to hit your right heel with the back side of the clubhead while you thrust your mid-section out toward the ball like Madonna on crack.
The solution: The Manzella-Special, towel plane board.