till tapper noun in a casino, a person who steals coins or tokens from a slot machine being played by someone else US,1999
They just grab it and walk out. We call these guys till-tappers. — Harry King, BoxMan, p. 82, 1972
I once caught a till tapper at the Tropicana in Las Vegas when he was reaching into the till on the slot machine that my wife was playing. — Charles W. Lund, RobbingtheOne-ArmedBandits, p. 122, 1999