n 1. A means by which work is done; an implement or tool, especially a device or mechanism for scientific or professional purposes, as distinguished from an apparatus, tool, or mechanism for industrial use. 2. Any means of accomplishment; The hands are instruments of the will. 3. A mechanical or other contrivance for the production of musical sounds. 4. A person doing the will of another. 5. Law A formal document, as a contract, deed, etc. See synonyms under AGENT, RECORD, TOOL

--Funk & Wagnalls Standard Dictionary