device vs fast one

device and fast one both are nouns.

Word	Noun	Adjective	Verb	Adverb
device	Yes	No	No	No
fast one	Yes	No	No	No

As nouns, fast one is a hyponym of device; that is, fast one is a word with a more specific, narrower meaning than device:

Other hyponyms of device include mnemonic, trick.

device (noun)	fast one (noun)
any clever maneuver	a cunning or deceitful action or device
an instrumentality invented for a particular purpose
an emblematic design (especially in heraldry)
any ornamental pattern or design (as in embroidery)
something in an artistic work designed to achieve a particular effect