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