crumb up

(slang, transitive) To ruin (something).

(transitive, slang, idiomatic, mildly, profane) To ruin, botch, bungle; to make a mess of.

An old slang phrase with two distinct meanings: originally it meant to delouse someone or treat them for lice — a very practical activity in wartime and barracks slang. It also evolved to mean ruining or messing something up badly, much like 'screw up' or 'balls up.' The second meaning is the more relatable one for modern audiences — when you crum up a plan, a presentation, or a relationship, you've thoroughly wrecked it through incompetence or bad luck.

(slang) To delouse; to treat for lice.

(idiomatic, slang, mildly, _, profane) To go wrong; to foul up; to make a mistake.