accessory noun

1 extra item

ADJ. essential, perfect, useful This silk scarf is the perfect accessory for stylish summer evenings. | bathroom, car, fashion

2 person who helps in crime

PREP. ~ to an accessory to murder

PHRASES an accessory before/after the fact (= a person who knows about a crime before/after it was committed and protects the criminal) (law) If you were lying to the police, then you have been an accessory after the fact for all these years.