gag·ger \ˈgagə(r), -aag-, -aig-\noun (-s) 1.: one that gags; specifically: a workman who takes the bends out of rails at a straightening press with a steel gag 2. a.: a foundry lifter b.: a piece of iron used in a foundry mold to keep the sand or a core in place 3.: one that thinks up gags : joker, gagman