1. optional part: an optional part that may be fitted to something to perform an additional function or enhance performance
2. fashion article: an item of clothing that is worn or used for a fashionable effect with an outfit
3. law somebody who helps criminal: somebody who aids somebody else in committing a crime or avoiding arrest but who does not participate in the crime itself
adjective
Definition:
1. additional: supplementary or subsidiary to something more important
2. law assisting in crime: aiding a criminal act although not participating in the crime itself