It's been a long time since a lot of casinos used coins so I could be a little rusty on the terminology; it is when coins are diverted to the cabinet below, when they should have gone into the hopper creating excessive hopper fills. Seldom happened since the change to Bill Validators, most play was machine credits and then when cash out was hit, the machine paid out the coins - which would empty a machine. This would be an issue if the machine only accepted coins and they would be diverted instead of filling up the hopper for payout.