louse (lous)
n.

1. 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 various animals, including humans.
2. pl., lous·es (lous'ĭz). Slang. A mean or despicable person.

tr.v. Slang, loused, lous·ing, lous·es.
To bungle: loused the project; louse up a deal.

[Middle English, from Old English lūs.]

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The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.

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