Definition of know-everythingism in US English:

know-everythingism

noun

rare
  • The belief that one knows everything, or that it is possible to do so; pretension to universal knowledge.

Origin

Mid 19th century. From know + everything + -ism, probably after know-nothingism.

Pronunciation

know-everythingism

/nəʊˈɛvrɪθɪŋɪz(ə)m/