Messenger-at-Arms; an officer appointed by and under the control of the Lyon King-at-Arms. (See Lyon.) Messengers-at-arms are said to be subservient to the Supreme Courts of Session and Justiciary, and they are employed in executing all summonses and letters of diligence, both in civil and criminal matters. Our signet letters seem to have been devised by the judges of the King's Court to supply the ancient writs of the law, and they were constantly directed to messengers-at-arms, as sheriffs in that part. It is the character, therefore, of sheriff in that part which has placed this duty in the hands of messengers-at-arms.