bouncer

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

• noun Slang A person employed to expel disorderly persons from a public place, especially a bar.
• noun Baseball A ground ball hit in such a way that it bounces.

from The Century Dictionary.

• noun One who or that which bounces.
• noun Something big or large of its kind.
• noun A large, strong, vigorous person: as, she is a bouncer.
• noun A strong muscular fellow kept in a hotel, restaurant, or other public resort, to bounce or expel disorderly persons.
• noun A liar; a boaster; a bully.
• noun A barefaced lie.

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

• noun One who bounces; a large, heavy person who makes much noise in moving.
• noun Collog. A boaster; a bully.
• noun Collog. A bold lie; also, a liar.
• noun Something big; a good stout example of the kind.
• noun a person employed by a tavern, nightclub, or other place of public meeting, to eject persons who become violent or unruly.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun informal A member of security personnel employed by bars, nightclubs, etc to maintain order and deal with patrons who cause trouble.
• noun cricket A short-pitched ball that bounces up towards, or above the height of the batsman’s head.
• noun Internet An account or server (as with IRC and FTP) that invisibly redirects requests to another, used for anonymity or vanity.
• noun dated One who bounces; a large, heavy person who makes much noise in moving.
• noun slang, archaic A boaster; a bully.
• noun slang, archaic A bold lie.
• noun slang, archaic A liar.
• noun Something big; a good stout example of the kind.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a person whose duty is to throw troublemakers out of a bar or public meeting