olemus
ISO/IEC 27037:
digitaalseadme võimestiku laiendamiseks
ta külge ühendatud seade
= device attached to a digital device
in order to expand its functionality

Merriam-Webster, noun:
a device connected to a computer to provide communication (such as input and output) or auxiliary functions (such as additional storage)
https://en.wikipedia.org/wiki/Peripheral

vt ka
- välisseadmed