insect

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

• noun Any of numerous arthropod animals of the class Insecta, having an adult stage characterized by three pairs of legs and a body segmented into head, thorax, and abdomen and usually having one or two pairs of wings. Insects include the flies, crickets, mosquitoes, beetles, butterflies, and bees.
• noun Any of various other small, chiefly arthropod animals, such as spiders, centipedes, or ticks, usually having many legs. Not in scientific use.
• noun An insignificant or contemptible person.

from The Century Dictionary.

• noun A small, usually winged and many-legged, invertebrate creature whose body appears to consist of several segments: a term used in popular speech without exactitude, being applied not only to flies, fleas, dragon-flies, butterflies, moths, bees, wasps, crickets, grasshoppers, roaches, beetles, bugs, lice, and other familiar creatures properly called insects, but also, improperly, to other small creatures whose structure and relations are not popularly understood, as the so-called coral insect, which is an actinozoan.
• noun In zoology, any member of the class or other division of animals called Insecta; an arthropod; a condylopod; an articulated animal with articulated legs, especially one with six such legs; a hexapod. See Insecta and Hexapoda, 1.
• Of, pertaining to, or of the nature of an insect or insects: as, insect transformations; insect architecture.
• Like an insect in any respect; small; mean; contemptible.
• To seek or catch insects, as a bird does.

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

• adjective Of or pertaining to an insect or insects.
• adjective Like an insect; small; mean; ephemeral.
• noun (Zoöl.) One of the Insecta; esp., one of the Hexapoda. See insecta.
• noun (Zoöl.) Any air-breathing arthropod, as a spider or scorpion.
• noun (Zoöl.) Any small crustacean. In a wider sense, the word is often loosely applied to various small invertebrates.
• noun Fig.: Any small, trivial, or contemptible person or thing.
• noun a powder used for the extermination of insects; esp., the powdered flowers of certain species of Pyrethrum, a genus now merged in Chrysanthemum. Called also Persian powder.

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

• noun An arthropod in the class Insecta, characterized by six legs, up to four wings, and a chitinous exoskeleton.
• noun colloquial Any small arthropod similar to an insect including spiders, centipedes, millipedes, etc
• noun A contemptible or powerless person.

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

• noun small air-breathing arthropod
• noun a person who has a nasty or unethical character undeserving of respect