noun

1. 1. a thing by means of which something is done; means
   2. a person used by another to bring something about
2. a tool or implement, esp. one used for delicate work or for scientific or artistic purposes
3. any of various devices for indicating or measuring conditions, performance, position, direction, etc. or sometimes, for controlling operations, esp. in aircraft or rocket flight
4. any of various devices producing musical sound, as a piano, drum, violin, oboe, etc.
5. Law a formal document, as a deed, contract, etc.
6. Finance a written order or promise to pay a sum of money a negotiable instrument

Etymology: OFr < L instrumentum, a tool or tools, stock, furniture, dress < instruere: see instruct

transitive verb

1. to provide with instruments
2. Music to arrange (a composition) for instruments; orchestrate