noun

1. a person or thing that rubs, as in polishing, scraping, massaging, etc.

2. Etymology: from orig. use as an eraser

   an elastic substance produced by coagulating and drying the milky sap (latex) of various tropical plants, esp. a tree (Hevea brasiliensis) of the spurge family: now most often produced synthetically or by chemically altering latex to obtain desired characteristics for use in making automobile tires, electrical insulation, molded objects and parts, etc.: in pure form rubber is a white, unsaturated hydrocarbon, having the formula (CH)
3. something made of this substance; specif.,
   1. an eraser
   2. ☆ a low-cut overshoe
   3. Slang a condom
4. ☆ Baseball an oblong rubber slab set in the pitcher's mound: the pitcher's foot must touch the rubber as each pitch is thrown

adjective

intransitive verb