See insect in Webster's New World College Dictionary
noun
any of a large class (Insecta) of small arthropod animals characterized, in the adult state, by division of the body into head, thorax, and abdomen, three pairs of legs on the thorax, and, usually, two pairs of membranous wings, including beetles, bees, flies, wasps, and mosquitoes
popularly any small arthropod, usually wingless, including spiders, centipedes, pill bugs, and mites
an unimportant or contemptible person
See insect in American Heritage Dictionary 4
(ĭnˈsĕktˌ)
noun
a. Any of numerous usually small 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 two pairs of wings. Insects include the flies, crickets, mosquitoes, beetles, butterflies, and bees.
b. Any of various similar arthropod animals, such as spiders, centipedes, or ticks. See Regional Note at lightning bug.