cus·tom n
1: a practice common to many or to a particular place or institution; esp: a long-established practice that is generally recognized as having the force of law see also section 1983 compare usage
2 pl
a: duties, tolls, or imposts imposed by the law of a country on imports or exports
b usu sing in constr: the agency, establishment, or procedure for collecting such customs
Merriam-Webster’s Dictionary of Law. Merriam-Webster. 1996.