The act of permanently destroying someone’s kneecaps. Often done with a firearm (as popularised in film and television), a baseball bat or lead pipe or other blunt instrument, or a power drill (often used in conjunction with a countersunk drill bit and popular with the IRA).
A method of persuation or intimidation that originated from the I.R.A. (Irish Republican Army) where a person is held down and someone takes a 2x4 piece of wood with a nail stuck through it and beats the victims knees with it untill they rip his/her knee cap off or permanently damage it so they can never walk again and undergo serious pain and agony.
What the Irish IRA and PIRA did when other drug dealers got in their way, they'd take a pistol and shoot him right in the back of the knee. This would shatter the knee, thus crippling the victim for life.