As a proper noun grass
is .
As a noun rubber is
(uncountable) pliable material derived from the sap of the rubber tree; a hydrocarbon polymer of isoprene or
rubber can be (sports) a series of an odd number of games or matches of which a majority must be won (thus precluding a tie), especially a match consisting of the best of a series of three games in bridge or whist.
As a verb rubber is
to eavesdrop on a telephone call.