peripheral

Etymology

From peripher(y) + -al.

adj

1. On the periphery or boundary.
2. Beside the point.
3. Unimportant.
4. Auxiliary.
5. (neuroanatomy) Related to or located in the peripheral nervous system.
   We have isolated the gene encoding the Schwann cell glycoprotein P0, the major structural protein of the peripheral myelin sheath. 1 March 1988, “Isolation and analysis of the gene encoding peripheral myelin protein zero”, in Neuron, →DOI, page 73

noun

1. (computing) A peripheral device.
   Check your peripheral's manual for the information you'll need. 1984, Human Connection, Making MS-DOS & PC-DOS work for you
   Check your peripheral's owners' manual to see at what speed your peripheral transmits or receives information, and then record this on the DIP Switch Information chart in the column at the left. 1986, Ziff-Davis Publishing Company, (Please provide the book title or journal name)
   Turn on the Mac, and check your peripheral. Since you've already installed your device driver, it should be available where you need it.... 1994, Steve Birchall, Upgrading and repairing Macs
2. Peripheral vision.
   We hailed a cab. The moment we got in, she stared at me with how-can-a-man-be-so-cruel eyes. I felt her glare, saw some of its fiery glow in my peripheral. The heat made me glance her way. 2000, Eric Jerome Dicke, Milk in My Coffee
   He would hear the coach's admonition, "Always check your peripheral," after the ringing stopped in his ears. But before then, his eyes were fixed on the ball and a possible interception, not the receiver angling toward him. 2003, Kim Louise, The Glory of Love
   As I sat by the window and read, I caught sight of the mailman in my peripheral. 2013, Saye Z. B. Zonen, Finding My Frequency
   2014, Bill Ladson, "Zimmerman handles left field with ease -- and no E's" on MLB.com I was kind of looking at the ball, keeping him in my peripheral and all of sudden I see him closing in on the ball.