boring vs deadening

boring and deadening both are nouns.

Word	Noun	Adjective	Verb	Adverb
boring	Yes	Yes	No	No
deadening	Yes	Yes	No	No

As adjectives, boring and deadening are synonyms defined as:

boring and deadening: so lacking in interest as to cause mental weariness

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

boring (noun)	deadening (noun)
the act of drilling a hole in the earth in the hope of producing petroleum	the act of making something futile and useless (as by routine)
the act of drilling

boring (adjective)	deadening (adjective)
so lacking in interest as to cause mental weariness	so lacking in interest as to cause mental weariness