pong vs malodour

pong and malodour both are nouns.

Word	Noun	Adjective	Verb	Adverb
pong	Yes	No	No	No
malodour	Yes	No	No	No

As nouns, malodour is a hypernym of pong; that is, malodour is a word with a broader meaning than pong:

Other hypernyms of pong include fetor, foetor, malodor, mephitis, reek, stench, stink.

pong (noun)	malodour (noun)
an unpleasant smell	a distinctive odor that is offensively unpleasant