The act of really messing things up.

Past tense of making a major mistake

To commit a blatant heinously humiliating error.

to screw up

what white people say when they fuck up

Screwing the pooch is a nonsensical action that is being done while a major fuck up is occuring or has occured.

to fuck things up royally; originally used by U.S. naval aviators to mean "crash one's plane into the water"