Defensive /(?)/

De·fen·sive

Defensive

a.
  1. Serving to defend or protect; proper for defense; opposed to offensive; as, defensive armor.
    A moat defensive to a house.
  2. Carried on by resisting attack or aggression; -- opposed to offensive; as, defensive war.
  3. In a state or posture of defense.

Defensive

n.
  1. That which defends; a safeguard.
    Wars preventive, upon just fears, are true defensives.

Phrases & Compounds
To be on the defensive
to be or stand in a state or posture of defense or resistance, in opposition to aggression or attack.