(firearms, primarily of revolvers) Requiring only a trigger pull to both cock and fire.

(firearms) A trigger mechanism requiring a single pull to both cock and fire.

(group theory) A mapping of a mathematical group to the permutations of an object that is compatible with the group operation.

(euphemistic, of a military serviceperson) Killed during military combat. / (of military equipment, resources, etc.) Destroyed during military combat.

plural of affirmative action

(slang) To succeed at seducing another person into sexual activity.

The hero of a work of fiction containing action, whose heroism typically includes participation in that action.

(physics, quantum mechanics) The effect of a detector on the measurement being recorded.

plural of piece of the action

A cinema that shows mainstream action films.