Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
weightiness is a noun meaning "the relative importance granted to something". It carries 2 recorded senses.
the relative importance granted to something
“his opinion carries great weight”
“the progression implied an increasing weightiness of the items listed”
the property of being comparatively great in weight
“the heaviness of lead”
Forms marked · are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for weightiness come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.