a ball which goes into the gutter
A ball that leaves the lane and travels down the gutter.
Delivery which rolls off the lane into the gutter.
Applies to playing a 5-play machine or higher and completing a hand with ZERO credits. A variation of this is (say while playing a 10-play machine) you catch a paying hand only on the last (10th) hand - I then refer to that as a '10 pin'.