judge advocate

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

• noun A commissioned officer in the US Army, Air Force, or Navy assigned to the Judge Advocate General's Corps.
• noun A staff officer serving as legal adviser to a commander.
• noun An officer acting as prosecutor at a court-martial.

from The Century Dictionary.

• noun See advocate.

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

• noun US A commissioned officer acting as a lawyer to advise a court martial on points of law or to act as prosecutor.

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

• noun an officer assigned to the judge advocate general
• noun a staff officer serving as legal adviser to a military commander