gas bomb vs bomb

gas bomb and bomb both are nouns.

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

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

gas bomb: a bomb laden with chemical agents that are released when the bomb explodes
bomb: an explosive device fused to explode under specific conditions

Other hypernyms of gas bomb include chemical weapon.

gas bomb (noun)	bomb (noun)
a bomb laden with chemical agents that are released when the bomb explodes	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

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