ho-hum vs boring

ho-hum is not a noun while boring is a noun.

Word	Noun	Adjective	Verb	Adverb
ho-hum	No	Yes	No	No
boring	Yes	Yes	No	No

As adjectives, ho-hum and boring are synonyms defined as:

Other synonyms of ho-hum include deadening, dull, irksome, slow, tedious, tiresome, wearisome.

ho-hum (noun)	boring (noun)
	the act of drilling a hole in the earth in the hope of producing petroleum
	the act of drilling

ho-hum (adjective)	boring (adjective)
so lacking in interest as to cause mental weariness	so lacking in interest as to cause mental weariness