irony vs caustic remark

irony and caustic remark both are nouns.

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

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

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

Other synonyms of irony include sarcasm, satire.

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