1. Characteristic of war, soldiers, and aggressive warlike behavior: The town was under martial law.
2. Associated with the military or armed forces: The country maintains a martial or warlike attitude toward its neighbors.
3. Soldier-like in behavior, bearing, etc.: The old veteran had a martial attitude.

Mr. Brown's martial uniform makes him look older than he really is.

4. Etymology: Martial literally means "pertaining to Mars", the Roman god of war.

Martial may refer to anything related to a soldier, like a military uniform, or it can refer to someone who is antagonistic and warlike.

If Martial Law is declared in a country, it means that the military has taken control of that country.

Martial Arts refers to any of several fighting styles that include specified methods of training for combat, armed and unarmed; and it is performed as a sport, including boxing, karate, judo, etc.