Gum1  —n. 1 a viscous secretion of some trees and shrubs. B adhesive substance made from this. 2 us chewing gum. 3 = *gumdrop. 4 = *gum arabic. 5 = *gum-tree. —v. (-mm-) 1 (usu. Foll. By down, together, etc.) Fasten with gum. 2 apply gum to.  gum up colloq. Interfere with the smooth running of. [greek kommi from egyptian kemai]