Definition of "Instrument" :

noun: the means whereby some act is accomplished

"My greed was the instrument of my destruction."

noun: a device that requires skill for proper use

noun: any of various devices or contrivances that can be used to produce musical tones or sounds

noun: the semantic role of the entity (usually inanimate) that the agent uses to perform an action or start a process

noun: (law) a document that states some contractual relationship or grants some right

noun: a person used by another to gain an end

verb: address a legal document to

verb: write an instrumental score for

verb: equip with instruments for measuring, recording, or controlling