accessary /əkˈsɛs(ə)ɹi/adjective 1noun 1forms 3 adjective1 •Accompanying as a subordinate; additional; accessory; especially, uniting in, or contributing to, a crime, but not as chief actor. See accessory.To both their deaths shalt thou be accessary. — 1593 noun1 •Someone who accedes to some act, now especially a crime; one who contributes as an assistant or instigator to the commission of an offense. formsaccessaries · more accessary · most accessary