WordNet sense 1 (any of various synthetic elastic materials whose properties resemble natural rubber):

synthetic rubber

WordNet sense 2 (an elastic material obtained from the latex sap of trees (especially trees of the genera Hevea and Ficus) that can be vulcanized and finished into a variety of products):

caoutchouc, gum elastic, India rubber, natural rubber

WordNet sense 3 (an eraser made of rubber (or of a synthetic material with properties similar to rubber); commonly mounted at one end of a pencil):

rubber eraser, pencil eraser

WordNet sense 4 (contraceptive device consisting of a sheath of thin rubber or latex that is worn over the penis during intercourse):

condom, prophylactic, safe, safety

WordNet sense 5 (a waterproof overshoe that protects shoes from water or snow):

arctic, galosh, gumshoe, golosh

WordNet sense 6 (returned for lack of funds):

no-good

WordNet sense 7 (having undesirable or negative qualities):

bad

WordNet sense 8 (coat or impregnate with rubber):

rubberize, rubberise