1. [n]  the means whereby some act is accomplished; "my greed was the instrument of my destruction"; "science has given us new tools to fight disease"
2. [n]  a device that requires skill for proper use
3. [n]  any of various devices or contrivances that can be used to produce musical tones or sounds
4. [n]  the semantic role of the entity (usually inanimate) that the agent uses to perform an action or start a process
5. [n]  (law) a document that states some contractual relationship or grants some right
6. [n]  a person used by another to gain an end
7. [v]  address a legal document to
8. [v]  write an instrumental score for
9. [v]  equip with instruments for measuring, recording, or controlling

1. \In"stru*ment\, n. [F. instrument, L. instrumentum.
   See {Instruct}.]
   1. That by means of which any work is performed, or result is
      effected; a tool; a utensil; an implement; as, the
      instruments of a mechanic; astronomical instruments.
            All the lofty instruments of war.     --Shak.
   2. A contrivance or implement, by which musical sounds are
      produced; as, a musical instrument.
            Praise him with stringed instruments and organs.
                                                  --Ps. cl. 4.
            But signs when songs and instruments he hears.
                                                  --Dryden.
   3. (Law) A writing, as the means of giving formal expression
      to some act; a writing expressive of some act, contract,
      process, as a deed, contract, writ, etc. --Burrill.
   4. One who, or that which, is made a means, or is caused to
      serve a purpose; a medium, means, or agent.
            Or useful serving man and instrument, To any
            sovereign state.                      --Shak.
            The bold are but the instruments of the wise.
                                                  --Dryden.
   Syn: Tool; implement; utensil; machine; apparatus; channel;
        agent.
   

2. \In"stru*ment\, v. t.
   To perform upon an instrument; to prepare for an instrument;
   as, a sonata instrumented for orchestra.
   

To install devices or instructions into hardware or software to monitor the operation of a system or component.