contusion

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

• noun An injury in which the skin is not broken; a bruise.

from The Century Dictionary.

• noun The act of beating and bruising, or the state of being bruised.
• noun The act of reducing to powder or fine particles by beating or pounding.
• noun In surgery, a bruise; a hurt or injury to the flesh or some part of the body without breach of integument or apparent wound, as one inflicted by a blunt instrument or by a fall.

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

• noun The act or process of beating, bruising, or pounding; the state of being beaten or bruised.
• noun (Med.) A bruise; an injury attended with more or less disorganization of the subcutaneous tissue and effusion of blood beneath the skin, but without apparent wound.

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

• noun A wound, such as a bruise, in which the skin is not broken; often having broken blood vessels and discolouration

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

• noun an injury that doesn't break the skin but results in some discoloration
• noun the action of bruising