Defending and Dodging was a concept used in Fantasy Trip, found on pg 18 of Fantasy Trip Melee.
The effect was (when choosing it like a maneuver, similar to All-Out Defense in GURPS) that instead of rolling on 3d to hit, attackers had to roll 4d, making them more likely to fail.
Dodging could only be done by a disengaged character and only worked against missile/thrown attacks. It required no equipment.
Defending could only be done by an engaged character and only worked against melee attacks. It reflects parrying and requires a readied non-missile weapon.