adjective
[more ~; most ~] formal :not relating to the main or most important part
computers :connected to a computer but not an essential part of it
of or relating to the area that is to the side of the area you are looking at
medical :of or relating to the part of the nervous system that is separate from the brain and spinal cord
noun
plural -als
[count] computers :a piece of equipment (such as a printer, speaker, etc.) that is connected to a computer but is not an essential part of it