b home Josh Murfitt bulb [buhlb] –noun 1. Botany. a. a usually subterranean and often globular bud having fleshy leaves emergent at the top and a stem reduced to a flat disk, rooting from the underside, as in the onion and lily. b. a plant growing from such a bud. 2. any round, enlarged part, especially at the end of a cylindrical object: the bulb of a thermometer. 3. Electricity. a. the glass housing, in which a partial vacuum has been established, that contains the filament of an incandescent electric lamp. b. an incandescent or fluorescent electric lamp. a b c d e f g h i j k l m n o p q r s t u v w x y z bus bulge bungalow bulb bunny