gutter spare

When your bowling ball falls into the gutter, but still manages to get a spare. Usually when only one of the 7 or 10 pins are left standing from the previous frame.

I got 9 pins on the first ball, then I threw a gutter spare.

Person A: Did you see that? The ball rocked so far in the gutter that it clipped the 7 pin and I got a spare.
Person B: Yeah, dude! Nice gutter spare!