(Canadian football) A defensive back whose primary jobs are to cover the slotback on passing plays and prevent running plays from going to the outside.

(psychology) A psychological strategy used unconsciously by people to cope with harmful or stressful situations. / (evolutionary biology) An automatic reaction of the body against foreign antibodies.

plural of defense mechanism

(computing) The practice of planning for contingencies in the design stage of a project so as to make the misuse of the software impossible, or to minimise the negative consequences.

plural of defensive design

(programming) A form of defensive design aiming to ensure the continuing functioning of a piece of software in spite of unforeseeable usage of it.

(video games) A style of real-time strategy video game in which the player attempts to stop enemies from crossing a map by building traps to slow them down and towers or turrets which shoot at them as they pass within range.

Efforts to protect the citizens of a state from military attack.

(US, law) A legal defense in which the defendant claims to have committed a crime in the belief that he/she was not in the real world, but in a simulated reality.

(academy) The final step in earning a doctorate: an oral examination in which the doctorand publicly defends his/her thesis to the examiners.