class action vs lawsuit

class action and lawsuit both are nouns.

Word	Noun	Adjective	Verb	Adverb
class action	Yes	No	No	No
lawsuit	Yes	No	No	No

As nouns, lawsuit is a hypernym of class action; that is, lawsuit is a word with a broader meaning than class action:

class action: a lawsuit brought by a representative member of a large group of people on behalf of all members of the group
lawsuit: a comprehensive term for any proceeding in a court of law whereby an individual seeks a legal remedy

Other hypernyms of class action include case, causa, cause, suit.

class action (noun)	lawsuit (noun)
a lawsuit brought by a representative member of a large group of people on behalf of all members of the group	a comprehensive term for any proceeding in a court of law whereby an individual seeks a legal remedy