Fight back is a term used to describe a defensive action taken in response to an attack or aggression. RETALIATE (9 letters) means to take revenge or to respond with countermeasures. REPULSE (7 letters) means to reject or drive away by force. DEFEND (6 letters) means to protect from attack or harm. REPEL (5 letters) means to drive back or ward off an attack. RESIST (6 letters) means to withstand the force of something. Returnfire (10 letters) means to fire back in response to an attack. All of these terms refer to a defensive action taken in response to an attack or aggression.