massiveness vs ponderousness

massiveness and ponderousness both are nouns.

Word	Noun	Adjective	Verb	Adverb
massiveness	Yes	No	No	No
ponderousness	Yes	No	No	No

As nouns, massiveness and ponderousness are synonyms defined as:

Other synonyms of massiveness include heft, heftiness, ponderosity.

massiveness (noun)	ponderousness (noun)
an unwieldy largeness	the property of being large in mass
the property of being large in mass	an oppressive quality that is laborious and solemn and lacks grace or fluency