v.tr. Brit. sl. 1 tamper with (a racehorse) to prevent its winning. 2 get hold of (money etc.) dishonestly. 3 catch (a criminal). 4 secure the support of or weaken (a person) esp. by underhand means. 5 seize, grab.
[ prob. = dial. knobble, knubble knock, beat, f. KNOB ]