know-nothing

Essentially deverbal in nature, albeit not from a unitary phrasal verb. Compare do-nothing § Etymology.

know-nothing (not comparable)

1. Ignorant; characterized by foolish denial of facts or beliefs in that which is not true.
   • 2017 February 20, Paul Mason, “Climate scepticism is a far-right badge of honour – even in sweltering Australia”, in the Guardian‎^[1]:

     All over the world, know-nothing xenophobes are claiming – without evidence – that climate science is rigged.

know-nothing (plural know-nothings)

1. An ignorant person; one who lacks knowledge.

   Synonym: ignoramus

• know-nothingness