1. pl. lice (līs) Any of numerous small, flat-bodied, wingless biting or sucking insects of the order Phthiraptera, which live as external parasites on birds and mammals, including humans. The lice are sometimes classified together with the psocids in the order Psocodea.
2. pl. lous·es (lousĭz) Slang A mean or despicable person.
tr.v. loused, lous·ing, lous·es
To bungle. Often used with up: louse up a deal.
[Middle English, from Old English lūs; see lūs- in the Appendix of Indo-European roots.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.