human dynamo vs fireball

human dynamo and fireball both are nouns.

Word	Noun	Adjective	Verb	Adverb
human dynamo	Yes	No	No	No
fireball	Yes	No	No	No

As nouns, human dynamo and fireball are synonyms defined as:

Other synonyms of human dynamo include ball of fire, powerhouse.

human dynamo (noun)	fireball (noun)
a highly energetic and indefatigable person	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)