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Related to louse up: delouse
louse someone or something up
Inf. to ruin something; to mess someone or something up. You really loused me up! You got me in a real mess! Who loused up my scheme?
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.
To cause something to fail because of poor handling; botch something: The president loused up the merger, costing the company millions of dollars. Let me tell the story—you always louse it up.