Merriam-Webster's Collegiate® Dictionary, 11th Edition
RUB
I. verb (rubbed; rubbing)
Etymology: Middle English rubben; akin to East Frisian rubben to rub, scrape, Icelandic rubba to scrape
Date: 14th century
intransitive verb
1. to move along the surface of a body with pressure ; grate , b. to fret or chafe with or as if with friction, to cause discontent, irritation, or anger, to continue in a situation usually with slight difficulty , to admit of being rubbed (as for erasure or obliteration), transitive verb
1. to subject to or as if to the action of something moving especially back and forth with pressure and friction, b. to cause (a body) to move with pressure and friction along a surface, to treat in any of various ways by rubbing, to bring into reciprocal back-and-forth or rotary contact, annoy , irritate ,
II. noun
Date: 1586
1. an unevenness of surface (as of the ground in lawn bowling), obstruction , difficulty , something grating to the feelings (as a gibe or harsh criticism), something that mars serenity, the application of friction with pressure