(US) Of a warrant, raid, etc.: allowing police to enter a property without immediate prior notification of the residents, as by knocking or ringing a doorbell.

(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 knock-knock joke

plural of knock knock

a verbal emulation of a knocking sound

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

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.

present participle of knock

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