instrument n1 : a means or implement by which something is achieved, performed, or furthered [an of crime]
2 : a document (as a deed, will, bond, note, certificate of deposit, insurance policy, warrant, or writ) evidencing rights or duties esp. of one party to another under the law [no person is liable on an unless his signature appears thereon "Uniform Commercial Code "] [an indictment is a form of charging ]
: negotiable instrument
Source: Merriam-Webster's Dictionary of Law ©1996. Merriam-Webster, Incorporated. Published under license with Merriam-Webster, Incorporated.