A knock-knock joke

(colloquial, often childish) A phrase used to introduce a "knock knock joke" / (colloquial, often childish) A phrase used in lieu of knocking (e.g. on the door), when it is not possible to knock.

a verbal emulation of a knocking sound

plural of knock knock

An abrupt rapping sound, as from an impact of a hard object against wood. / A sharp impact. / (figuratively) A criticism. / (figuratively) A blow or setback.

(transitive, dated) To strike for admittance; to rap upon, as a door. / (transitive, colloquial) To criticize verbally; to denigrate; to undervalue.

(rugby) A foul in which a player knocks the ball forward. / (chiefly UK) Resulting as an indirect effect.

simple past tense and past participle of knock

present participle of knock

An act in which something is knocked on, or the sound thus produced