dumb bomb vs bomb

dumb bomb and bomb both are nouns.

Word	Noun	Adjective	Verb	Adverb
dumb bomb	Yes	No	No	No
bomb	Yes	No	Yes	No

As nouns, bomb is a hypernym of dumb bomb; that is, bomb is a word with a broader meaning than dumb bomb:

dumb bomb: a bomb that falls because of gravity and is not guided to a target
bomb: an explosive device fused to explode under specific conditions

dumb bomb (noun)	bomb (noun)
a bomb that falls because of gravity and is not guided to a target	an explosive device fused to explode under specific conditions
	strong sealed vessel for measuring heat of combustion
	an event that fails badly or is totally ineffectual

dumb bomb (verb)	bomb (verb)
	throw bombs at or attack with bombs
	fail to get a passing grade