Open English Wordnet
Nouns
(n)peripheral, computer peripheral, peripheral deviceelectronic equipment external to the circuit board that contains the CPU of a computer“disk drives and printers are important peripherals”
Adjectives
(a)peripheralon or near an edge or constituting an outer boundary; the outer area“Russia's peripheral provinces”, “peripheral suburbs”
(s)peripheralrelated to the key issue but not of central importance“a peripheral interest”, “energy is far from a peripheral issue in the economy”, “peripheral issues”