ho-hum vs deadening

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

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

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

ho-hum and deadening: so lacking in interest as to cause mental weariness

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

ho-hum (noun)	deadening (noun)
	the act of making something futile and useless (as by routine)

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