The knowledge and skill to be able to (do something correctly).

(chiefly US, derogatory) Someone who claims to be knowledgeable or an expert in something, obnoxiously dismissing the opinions, advice, suggestions, etc. of others.

Used other than figuratively or idiomatically: see you, know. / (informal) Expression signifying a pause or hesitation.

(informal) To be aware of a situation, especially of the consequences of misconduct.

(idiomatic) Indicates agreement, approval, encouragement.

(transitive) To become acquainted with (someone or something); to meet someone. / Used other than figuratively or idiomatically: see get, know.

(chiefly UK, Ireland) Someone who obnoxiously claims to be knowledgeable on a subject.

plural of know-nothing

Ignorant; characterized by foolish denial of facts or beliefs in that which is not true.

An ignorant person; one who lacks knowledge.