I. louse 1 /laʊs/ BrE AmE noun [countable]
[ Language: Old English ; Origin: lus ]
1 . ( plural lice /laɪs/) a small insect that lives on the hair or skin of people or animals
2 . ( plural louses ) informal someone who is nasty and unpleasant
II. louse 2 BrE AmE verb
louse something ↔ up phrasal verb informal
to make something worse rather than better, or to spoil something SYN mess up :
That idiot loused up my chance of promotion.