"ponderousness" in the noun sense
1. ponderousness, heaviness
an oppressive quality that is laborious and solemn and lacks grace or fluency
"a book so serious that it sometimes subsided into ponderousness"
"his lectures tend to heaviness and repetition"
2. heft, heftiness, massiveness, ponderousness, ponderosity
the property of being large in mass
Source: WordNet® (An amazing lexical database of English)
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