ho-hum vs irksome

ho-hum and irksome both are adjectives.

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

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

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

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