looker-on vs looker

looker-on and looker both are nouns.

Word	Noun	Adjective	Verb	Adverb
looker-on	Yes	No	No	No
looker	Yes	No	No	No

As nouns, looker is a hypernym of looker-on; that is, looker is a word with a broader meaning than looker-on:

looker-on: someone who looks on
looker: a close observer; someone who looks at something (such as an exhibition of some kind)

Other hypernyms of looker-on include spectator, viewer, watcher, witness.

looker-on (noun)	looker (noun)
someone who looks on	a very attractive or seductive looking woman
	a close observer; someone who looks at something (such as an exhibition of some kind)