coup vs countercoup

coup and countercoup both are nouns.

Word	Noun	Adjective	Verb	Adverb
coup	Yes	No	No	No
countercoup	Yes	No	No	No

As nouns, countercoup is a hyponym of coup; that is, countercoup is a word with a more specific, narrower meaning than coup:

coup: a sudden and decisive change of government illegally or by force
countercoup: a sudden and decisive overthrow of a government that gained power by a coup d'etat

coup (noun)	countercoup (noun)
a sudden and decisive change of government illegally or by force	a sudden and decisive overthrow of a government that gained power by a coup d'etat
a brilliant and notable success