1. [techspeak] During the execution of a procedural language, one is said to unwind the stack from a called procedure up to a caller when one discards the stack frame and any number of frames above it, popping back up to the level of the given caller. In C this is done with longjmp/setjmp, in LISP or C++ with throw/catch. See also smash the stack.
2. People can unwind the stack as well, by quickly dealing with a bunch of problems: “Oh heck, let's do lunch. Just a second while I unwind my stack.”