caustic remark vs irony

caustic remark and irony both are nouns.

Word	Noun	Adjective	Verb	Adverb
caustic remark	Yes	No	No	No
irony	Yes	No	No	No

As nouns, caustic remark and irony are synonyms defined as:

caustic remark and irony: witty language used to convey insults or scorn

Other synonyms of caustic remark include sarcasm, satire.

caustic remark (noun)	irony (noun)
witty language used to convey insults or scorn	incongruity between what might be expected and what actually occurs
	a trope that involves incongruity between what is expected and what occurs
	witty language used to convey insults or scorn