third-rater vs actor

third-rater and actor both are nouns.

Word	Noun	Adjective	Verb	Adverb
third-rater	Yes	No	No	No
actor	Yes	No	No	No

As nouns, actor is a hypernym of third-rater; that is, actor is a word with a broader meaning than third-rater:

Other hypernyms of third-rater include doer, worker.

third-rater (noun)	actor (noun)
one who is third-rate or distinctly inferior	a theatrical performer
	a person who acts and gets things done