self defence The act of defending oneself or something that belongs or relates to oneself. Every person is justified in using reasonable force to defend himself and those under his care, but the force justifiable is such only as is reasonably necessary. Every person has a right to defend his own body and the body of any other person as well as the right to defend his own property and the property of any other person. And this is known as the right of private defence. Nothing is an offence which is done in the exercise of the right of private defence.