fireball vs human dynamo

fireball and human dynamo both are nouns.

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

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

Other synonyms of fireball include ball of fire, powerhouse.

fireball (noun)	human dynamo (noun)
the luminous center of a nuclear explosion	a highly energetic and indefatigable person
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)