ill-smelling vs malodourous

ill-smelling and malodourous both are adjectives.

Word	Noun	Adjective	Verb	Adverb
ill-smelling	No	Yes	No	No
malodourous	No	Yes	No	No

As adjectives, ill-smelling and malodourous are synonyms defined as:

Other synonyms of ill-smelling include malodorous, stinky, unpleasant-smelling.

ill-smelling (adjective)	malodourous (adjective)
having an unpleasant smell	having an unpleasant smell