copper's nark vs squealer

copper's nark and squealer both are nouns.

Word	Noun	Adjective	Verb	Adverb
copper's nark	Yes	No	No	No
squealer	Yes	No	No	No

As nouns, squealer is a hypernym of copper's nark; that is, squealer is a word with a broader meaning than copper's nark:

copper's nark: an informer or spy working for the police
squealer: one who reveals confidential information to the police or other authority

Other hypernyms of copper's nark include betrayer, blabber, informer, rat.

copper's nark (noun)	squealer (noun)
an informer or spy working for the police	domestic swine
	one who reveals confidential information to the police or other authority