adj. Related to, located in, or constituting an outer boundary or periphery.adj. Perceived or perceiving near the outer edges of the retina: peripheral vision. adj. Anatomy Of the surface or outer part of a body or organ; external.adj. Anatomy Of, relating to, or being part of the peripheral nervous system.adj. Of minor relevance or importance.adj. Auxiliary.n. Computer Science An auxiliary device, such as a printer, modem, or storage system, that works in conjunction with a computer.