say it: ruh-BEL-ee-uh-snuhs
rebelliousness is a noun meaning "intentionally contemptuous behavior or attitude". It carries 2 recorded senses.
intentionally contemptuous behavior or attitude
an insubordinate act
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 rebelliousness come from Princeton University’s WordNet. The pronunciation comes from the CMU Pronouncing Dictionary. Commonness is measured against a corpus of everyday English. Full sources and licences.