To destroy, damage, wreck, ruin, or generally f*** something up to the point that it's unusable, or to f*** someone up or pop a cap in their ass. Can also be used to refer to doping a racehorse or an athlete.

"What's the betting someone tries to knobble Golden Thunder before tomorrow's big race?" (Racehorse/Doping)

"I don't give a rat's ass whether he apologized. I want you to go and knobble Sammy the Squealer. Give him a long wet nap." (Mafia/Gangster/destroying someone)

A term used to reference cannabis/marijuana/weed.

Small knob aka micropenis or prepubescent dick.

the knob at the end of your penis.

Slang word for 'Knob'.