atomic explosion vs fireball

atomic explosion and fireball both are nouns.

Word	Noun	Adjective	Verb	Adverb
atomic explosion	Yes	No	No	No
fireball	Yes	No	No	No

atomic explosion (noun)	fireball (noun)
the explosion of an atomic bomb	the luminous center of a nuclear explosion
	a ball of fire (such as the sun or a ball-shaped discharge of lightning)
	a highly energetic and indefatigable person
	an especially luminous meteor (sometimes exploding)