louse

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun 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.
• noun Slang A mean or despicable person.
• transitive verb To bungle. Often used with up.

from The Century Dictionary.

• A Middle English variant of loose.
• noun An insect or other small arthropod (as a crustacean) that infests other animals or plants, or an animal resembling such parasites: a name for a great variety of small creatures.
• noun Bird-lice are parasitic insects, of several hundred species, various genera, and several families, which some authors range with the foregoing in the order Hemiptera, but most place in the Pseudoneuroptera. They are known as the order or superfamily Mallophaga. They have mandibulate or biting mouth-parts, are wingless, and of very variable forms. They are by no means confined to birds, but infest mammals as well; almost every kind of bird and beast is infested by these creatures, sometimes several species to one host, and in such multitudes as to canse disease and death. Of these, such as infest domestic quadrupeds and birds belong to the genera Trichodectes, Docophorus, Nirmus, Goniocotes, Goniodes, Lipeurus, Trinotum, Colpopocephalum, Menopon, and Gyropus.
• noun The beaver harbors a remarkable louse, Platypsyllus castoris, a degraded clavicorn beetle, so peculiar as to have been made type of an order, Achreioptera.
• noun Insects have their own lice. Such are the bee-lice, or pupiparous dipterous insects of the family Braulidæ, order Diptera; and some of the lice of bats are similar dipterous insects, though wingless, of the family Nycteribiidæ. Bees, wasps, etc., are also infested by certain small parasitic heteromerous beetles in the form of lice, such as the wingless larvæ of Meloidæ, a species of which has been named Pediculus melittæ, and the whole family Stylopidæ. Insects affected by the latter are said to be stylopized. None of the foregoing lice are aquatic.
• noun Fishes, marine mammals. crustaceans, etc., are infested by a great variety of small degraded crustaceans, collectively known as fish-lice or Ichthyophthira. Most of these belong to a class or order Epizoa or Siphonostoma, or Lernæoidea; a few are cirripeds, as Rhizocephala. Whale-lice are Cyamidæ. Carpice are Argulidæ.
• noun Wood-lice are the terrestrial isopods of the family Oniscidæ, also called slaters, sow-bugs, etc. These are not parasites, but some of the aquatic isopods are fish-lice, as Cymothoidæ.
• noun Plants are infested by multitudes of small plant-sucking hemipters, known as plant-lice, and formerly collectively termed Phytophthiria: as the aphids, Aphididæ, some of which are also called gall-lice; the psyllids, Psyllidæ, called flea-lice and jumping plant-lice; and the scale-insects or Coccidæ, some of which are also known as bark-lice.
• noun Book-lice are pseudoneuropterous insects of the family Psocidæ, various species of which, as those of the genera Atropos and Clothilla, injure books.
• noun Certain mites or acarids are sometimes called lice, as the harvest-ticks, known as red-lice, the itch-mite or itch-louse, etc. For further information, see the compounded words, and also the technical names.
• To clean from lice.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Zoöl.) Any one of numerous species of small, wingless, suctorial, parasitic insects belonging to a tribe (Pediculina), now usually regarded as degraded Hemiptera. To this group belong of the lice of man and other mammals. See Crab louse, Dog louse, Cattle louse, etc., under crab, dog, etc.
• noun Any one of numerous small mandibulate insects, mostly parasitic on birds, and feeding on the feathers. They are known as Mallophaga, or bird lice, though some occur on the hair of mammals. They are usually regarded as degraded Pseudoneuroptera. See Mallophaga.
• noun Any one of the numerous species of aphids, or plant lice. See Aphid.
• noun Any small crustacean parasitic on fishes. See Branchiura, and Ichthvophthira.
• noun (Zoöl.) a parasitic dipterous insect of the group Pupipara. Some of them are wingless, as the bee louse.
• noun (Zoöl.) any one of numerous species of mites which infest mammals and birds, clinging to the hair and feathers like lice. They belong to Myobia, Dermaleichus, Mycoptes, and several other genera.
• transitive verb To clean from lice.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A small parasitic wingless insect of the order Phthiraptera.
• noun colloquial, dated A contemptible person; one who has recently taken an action considered deceitful or indirectly harmful.
• verb To remove lice from the body of a person or animal; to delouse.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun any of several small insects especially aphids that feed by sucking the juices from plants
• noun a person who has a nasty or unethical character undeserving of respect
• noun wingless insect with mouth parts adapted for biting; mostly parasitic on birds
• noun wingless usually flattened bloodsucking insect parasitic on warm-blooded animals