There's always stuff in the way to louse up a good flight plan.
All you did was louse up a perfectly promising fracas so far as they were concerned.
She'd be shocked to her sweet little core, and she'd louse up the whole deal.
"parasitic insect infecting human hair and skin," Old English lus, from Proto-Germanic *lus (cf. Old Norse lus, Middle Dutch luus, Dutch luis, Old High German lus, German Laus), from PIE *lus- "louse" (cf. Welsh lleuen "louse"). Slang meaning "obnoxious person" is from 1630s. The plural lice (Old English lys) shows effects of i-mutation. The verb meaning "to clear of lice" is from late 14c.; to louse up "ruin, botch" first attested 1934, from the literal sense (of bedding), from 1931.
n. pl. lice (līs)
Any of numerous small, flat-bodied, wingless biting or sucking insects of the orders Mallophaga or Anoplura, many of which are external parasites on humans.