"Top chopping" Lowering the roof by shortening the posts.
"Body sectioning" or usually simply "sectioning" is lowering the body by cutting and removing a portion of it horizontally, like a top chop to the body it's self, usually right thru the middle of the doors, quarters, and fenders HORIZONTALLY.
"Channeling" is when you cut the floor out and lower the body over the frame.
"Frenching" is moulding in or "Smoothing" anything. "Frenched" headlamps are where you weld in the head lamp ring so the head lamp glass is all you see. "Frenching" an ant is removing the nut in some way.
"Tunneling" is where you Tunnel something in using tubing or a home made "tunnel" to tuck something back into the body. "Tunneled" antenna is where you would use exhaust tubing or similar and weld a washer on the bottom and weld the tube into the car so that the antenna is sitting in a tunnel. (click here for how to)
"Tunneling" headlamps or taillamps is the same thing, "sinking" them into the body.
"Shaving" is simply removing and welding or moulding off the holes. You would "Shave" emblems, bolts on a bumper, etc.
These and other terms can be regional as well. Someone in New York may use completely different terms but these would be understood.