Definition of thickheadedness in US English:

thickheadedness

noun

informal
  • See thickheaded

    • ‘He is openly contemptuous of democracy, falling back on arguments about the invincible thickheadedness of many people.’
    • ‘Cushing's running commentary is sympathetic to Castro's revolution, but even he notes that ‘almost every designer has anecdotes of creative work thwarted by political inappropriateness or bureaucratic thickheadedness.’’
    • ‘It was drizzling more heavily now and Croft turned up his coat collar, cursing the watchman's thickheadedness.’
    • ‘Ph.Ds, high IQs, and intellectual honors are not antidotes to thickheadedness.’

Pronunciation

thickheadedness

/ˌθɪkˈhɛdədnəs//ˌTHikˈhedədnəs/