What is Se Defendendo?

Legal Definition
"Self-defense". The act of defending one's own person or property, or the well-being or property of another.
Legal Definition
Criminal law. Defending himself.

2. Homicide, se defendendo, is that which takes place upon a sudden rencounter, where two persons upon a sudden quarrel, without premeditation or malice, fight upon equal terms, and one, before a mortal stroke has been given, declines any further combat, and retreats as far as he can with safety, and kills his adversary, through necessity, to avoid immediate death. 2 Swift's Dig. 289 pamphl. Rep. of Selfridge's, Trial in, 1805 Hawk. bk. 1, c. 11, s. 13; 2 Russ. on Cr. 543; Bac. Ab. Murder, &c F 2.
-- Bouviers Law Dictionary
Legal Definition
Lat. In defending himself; in self-defense. Homicide committed se defendendo is excusable.
-- Black's Law Dictionary
Legal Definition
In self-defense.
-- Ballentine's Law Dictionary