external cutter

1. n. [Well Workover and Intervention]
A downhole tool used to cut tubing or similar tubulars that have become stuck in the wellbore. The external cutter slips over the fish or tubing to be cut. Special hardened metal-cutters on the inside of the tool engage on the external surfaces of the fish. External cutters are generally used to remove the topmost, possibly damaged, portion of a fish to enable an overshot, or similar fishing tools, to engage on an undamaged surface.