dumb bomb vs gravity bomb

dumb bomb and gravity bomb both are nouns.

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

As nouns, dumb bomb and gravity bomb are synonyms defined as:

dumb bomb and gravity bomb: a bomb that falls because of gravity and is not guided to a target

dumb bomb (noun)	gravity bomb (noun)
a bomb that falls because of gravity and is not guided to a target	a bomb that falls because of gravity and is not guided to a target