Definition of nincompoopery in English:

nincompoopery

noun

informal
  • Foolishness, stupidity; the action, speech, or behaviour of a nincompoop.

Origin

Mid 19th century. From nincompoop + -ery.

Pronunciation

nincompoopery

/ˈnɪŋkəmpuːpəri//ˌnɪŋkəmˈpuːpəri/