Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
pretentiousness is a noun meaning "lack of elegance as a consequence of being pompous and puffed up with vanity". It carries 2 recorded senses.
lack of elegance as a consequence of being pompous and puffed up with vanity
the quality of being pretentious (behaving or speaking in such a manner as to create a false appearance of great importance or worth)
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 pretentiousness come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.