boring vs ho-hum

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

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

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

Other synonyms of boring include deadening, dull, irksome, slow, tedious, tiresome, wearisome.

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

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