"Cocked and locked" refers to a method of carrying a pistol, often a 1911 gov't model semiauto, with a round already
in the chamber and
the hammer cocked back and ready to fire. It is a term coined by police who carry 1911 pistols in this manner. Usually the holster strap is inserted between the hammer and firing pin for safety, which is snapped open when needed for a fast draw. It is actually safe to carry a 1911 model pistol in this way because of the redundant safety mechanisms such as the 1911's grip safety and thumb safety to protect against any
accidental discharge until the weapon is on target and the shooter is ready to fire.
I like to carry my 1911 Colt
Commander "cocked and locked" in my concealment holster when I go out. I want to be
instantly ready for action if I have to draw. Having to rack your slide before firing could
potentially get you killed.