say it: stoo-PID-i-tee
stupidity is a noun meaning "a poor ability to understand or to profit from experience". It carries 2 recorded senses.
a poor ability to understand or to profit from experience
a stupid mistake
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 stupidity 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.