ACCESSORY Copy link • ACCESSORY 1. adj. Vid: ADDITIONAL. 2. s. alicujus rei or alicui rei affinis (e.g., facinori, noxae, etc.): conscius: correus (a legal term for one put on his trial at the same time on the same charge, Ulp.): particeps alicujus rei (e.g., conjurationis): socius (e.g., sceleris). These words do not express an accessory as opposed to a principal.