bump

from The American Heritage® Dictionary of the English Language, 5th Edition.

• intransitive verb To strike or collide with.
• intransitive verb To cause to knock against an obstacle.
• intransitive verb To knock to a new position; shift.
• intransitive verb To shake up and down; jolt.
• intransitive verb To displace from a position within a group or organization.
• intransitive verb To deprive (a passenger) of a reserved seat because of overbooking.
• intransitive verb To raise; boost.
• intransitive verb Sports To pass (a volleyball) by redirecting it with the forearms.
• intransitive verb To hit or knock against something.
• intransitive verb To proceed with jerks and jolts.
• intransitive verb Sports To bump a volleyball.
• noun A blow, collision, or jolt.
• noun The sound of something bumping.
• noun A raised or rounded spot; a bulge.
• noun A slight swelling or lump.
• noun A rise or increase, as in prices or enrollment.
• noun A forward thrust of the pelvis, as in a burlesque striptease.
• noun Sports A pass in volleyball made by redirecting the ball with the inside of the forearms, especially when extended and held together.
• noun Slang A shot of hard liquor, sometimes accompanied by a beer chaser.

from The Century Dictionary.

• noun A booming, hollow noise.
• noun A shock from a collision, such as from the jolting of a vehicle.
• noun In English boat-racing, the striking of one boat by the prow of another following her. See bump, transitive verb, 2.
• noun A swelling or protuberance, especially one caused by a blow.
• noun Specifically The popular designation of the natural protuberances on the surface of the skull or cranium, which phrenologists associate with distinct qualities, affections, propensities, etc., of the mind: used ironically for the word organ employed by phrenologists: as, the bump of veneration, acquisitiveness, etc.
• noun The corner of the stock of a gun at the top of the heel-plate.
• To make a loud, heavy, or hollow noise, as the bittern; boom.
• To cause to come in violent contact; bring into concussion; knock; strike; thump: as, to bump one's head against a wall.
• In English boat-racing, to touch (the stern of a boat ahead) with the bow of the following boat. See extract.
• To come forcibly in contact with something; strike heavily: as, the vessel bumped against the wharf.
• To ride without rising in the stirrups on a rough-trotting horse.
• In chem., to give off vapor intermittently and with almost explosive violence, as some heated solutions.
• To form bumps or protuberances.
• noun In cricket, the act of rising higher than usual from the pitch after being bowled: said of the ball.
• noun A material used for coarse sheets.
• noun In London, a sort of matting used for covering floors.

from the GNU version of the Collaborative International Dictionary of English.

• intransitive verb To come in violent contact with something; to thump.
• intransitive verb To make a loud, heavy, or hollow noise, as the bittern; to boom.
• noun A thump; a heavy blow.
• noun A swelling or prominence, resulting from a bump or blow; a protuberance.
• noun (Phren.), colloq. One of the protuberances on the cranium which are associated with distinct faculties or affections of the mind
• noun engraving The act of striking the stern of the boat in advance with the prow of the boat following.
• transitive verb To strike, as with or against anything large or solid; to thump.
• noun The noise made by the bittern.