noun Something done, often so as to accomplish a purpose.
noun A way of motion or functioning.
Knead bread with a rocking action.
noun Fast-paced activity.
a movie full of exciting action
noun The way in which a mechanical device acts when used; especially a firearm.
Pressing a piano key causes the action of the hammer on the string.
noun The way in which cartridges are loaded, locked, and extracted from the mechanism.
pump-action shotgun
noun A physical mechanism of a firearm or other device.
noun The mechanism, that is the set of moving mechanical parts, of a keyboard instrument, like a piano, which transfers the motion of the key to the sound-making device.
The run in bar 12 is almost impossible with this piano's heavy action.