Princeton's WordNet

1. rubber, natural rubber, India rubber, gum elastic, caoutchouc(noun)

   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

   Synonyms:
   prophylactic, pencil eraser, condom, safety, galosh, safe, natural rubber, rubber eraser, golosh, arctic, gumshoe, synthetic rubber, rubber, caoutchouc, gum elastic

   Antonyms:
   good

2. rubber, synthetic rubber(noun)

   any of various synthetic elastic materials whose properties resemble natural rubber

   Synonyms:
   prophylactic, pencil eraser, condom, safety, galosh, safe, natural rubber, rubber eraser, golosh, arctic, gumshoe, synthetic rubber, rubber, caoutchouc, gum elastic

   Antonyms:
   good

3. rubber eraser, rubber, pencil eraser(noun)

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

   Synonyms:
   prophylactic, pencil eraser, condom, safety, galosh, safe, natural rubber, rubber eraser, golosh, arctic, gumshoe, synthetic rubber, rubber, caoutchouc, gum elastic

   Antonyms:
   good

4. condom, rubber, safety, safe, prophylactic(noun)

   contraceptive device consisting of a sheath of thin rubber or latex that is worn over the penis during intercourse

   Synonyms:
   condom, caoutchouc, base hit, preventive, safe, guard, arctic, safety, safety device, rubber, refuge, pencil eraser, golosh, preventative, rubber eraser, gumshoe, synthetic rubber, galosh, gum elastic, prophylactic, natural rubber

   Antonyms:
   good

5. arctic, galosh, golosh, rubber, gumshoe(adj)

   a waterproof overshoe that protects shoes from water or snow

   Synonyms:
   condom, caoutchouc, safe, arctic, safety, hawkshaw, rubber, pencil eraser, golosh, dick, rubber eraser, gumshoe, synthetic rubber, galosh, gum elastic, prophylactic, natural rubber

   Antonyms:
   good

6. rubber, no-good(verb)

   returned for lack of funds

   Synonyms:
   no-good, meritless, sorry, no-count, rubber, good-for-naught, good-for-nothing, no-account

   Antonyms:
   good

7. rubberize, rubberise, rubber(verb)

   coat or impregnate with rubber

   Synonyms:
   rubber, rubberize, rubberise

   Antonyms:
   good