meaning vs subject matter

meaning and subject matter both are nouns.

Word	Noun	Adjective	Verb	Adverb
meaning	Yes	Yes	No	No
subject matter	Yes	No	No	No

As nouns, subject matter is a hypernym of meaning; that is, subject matter is a word with a broader meaning than meaning:

Other hypernyms of meaning include content, message, substance.

meaning (noun)	subject matter (noun)
the idea that is intended	content communicating a message; what something is about
the message that is intended or expressed or signified

meaning (adjective)	subject matter (adjective)
rich in significance or implication