A bedbug is a small insect with a round body and no wings which lives in dirty houses and feeds by biting people and sucking their blood when they are in bed. an insect that sucks blood and lives in dirty houses, especially in beds. Any member of approximately 75 species of nocturnal insects (family Cimicidae) that feed by sucking the blood of humans and other warm-blooded animals. The reddish brown adult is broad and flat and less than 0.2 in. (4-5 mm) long. Among the most cosmopolitan of human parasites, they are found in every kind of dwelling. They digest meals slowly; adults have lived for at least a year without food. Though the bite is irritating, it is not known to transmit diseases to humans