dishonorable discharge

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

• noun Expulsion from the armed services and denial of veterans' benefits resulting from a court-martial conviction of a serious violation of the military code, such as failure to obey orders, desertion, rape, or murder.

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

• noun a discharge from the armed forces for a grave offense (as sabotage or espionage or cowardice or murder)