Spoil, ruin, bungle. For example, The bad weather loused up our plans, or Your change of mind really loused me up. This slangy expression originated in World War I, when infestation with lice was the common lot of soldiers in the trenches; its figurative use dates from the 1930s.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
How to use louse up in a sentence
She'd be shocked to her sweet little core, and she'd louse up the whole deal.The Galaxy Primes | Edward Elmer Smith
All you did was louse up a perfectly promising fracas so far as they were concerned.Frigid Fracas | Dallas McCord Reynolds
There's always stuff in the way to louse up a good flight plan.Eight Keys to Eden | Mark Irvin Clifton