pe·riph·er·al 
(pə-rĭfər-əl)
(pə-rĭfər-əl)adj.
1. Related to, located in, or constituting an outer boundary or periphery.
2. Perceived or perceiving near the outer edges of the retina: peripheral vision.
3. Anatomy
a. Of the surface or outer part of a body or organ; external.
b. Of, relating to, or being part of the peripheral nervous system.
4. Of minor relevance or importance.
5. Auxiliary.
n.
Computers
Computers
An auxiliary device, such as a printer, modem, or storage system, that works in conjunction with a computer.
pe·ripher·al·ly adv.