couch potato vs idler

couch potato and idler both are nouns.

Word	Noun	Adjective	Verb	Adverb
couch potato	Yes	No	No	No
idler	Yes	No	No	No

As nouns, idler is a hypernym of couch potato; that is, idler is a word with a broader meaning than couch potato:

couch potato: an idler who spends much time on a couch (usually watching television)
idler: person who does no work

Other hypernyms of couch potato include bum, do-nothing, layabout, loafer.

couch potato (noun)	idler (noun)
an idler who spends much time on a couch (usually watching television)	person who does no work