One of a class of childish jokes told as a dialog, and usually including a pun, in the following form:

(UK, Ireland, Australia, New Zealand, slang) Tired or exhausted.

simple past tense and past participle of knacker

(UK, Ireland, South Africa, colloquial) Broken, inoperative.

(baseball) To cause a pitcher to be replaced by heavy hitting. / (idiomatic) To cause something to be replaced by something else.

(anatomy) The flat, roundish bone in the knee. / (roofing) A metal cover trim that fits over a panel rib after it has been cut and bent.

(transitive) To destroy the knees of (a person), usually by shooting at the knees, as a punishment carried out by criminals or terrorists.

A compact folding knife. / The front-dive pike, in which the body folds and unfolds. / (colloquial) A semi-trailer truck accident in which the vehicle mimics the closing of a jack-knife.

To fold in the middle, as a jackknife does. / (colloquial) To cause a semi-trailer truck to fold like a jackknife in a traffic accident.

(chiefly US) A case of canvas or leather, for carrying items on the back. / (cryptography) A set of values from which a subset is chosen.