pertaining to, situated in, or constituting the periphery

peripheral resistance on the outskirts of the battle area.

concerned with relatively minor, irrelevant, or superficial aspects of the subject in question.

Anatomy . near the surface or outside of; external.

Computers . of or pertaining to a peripheral.

Computers . a device or unit that operates separately from the CPU but is connected to it, as a magnetic disk or tape unit or a printer.

adjective

central , crucial , internal , major

adjective

beside the point , borderline , exterior , external , incidental , inessential , irrelevant , minor , outer , outermost , perimetric , secondary , superficial , surface , tangential , unimportant , circumferential , distal , distant , marginal , peripheric