Knock  —v. 1 a strike with an audible sharp blow. B (often foll. By at) strike (a door etc.) To gain admittance. 2 make (a hole etc.) By knocking. 3 (usu. Foll. By in, out, off, etc.) Drive (a thing, person, etc.) By striking (knocked the ball into the hole; knocked those ideas out of him). 4 slang criticize. 5 a (of an engine) make a thumping or rattling noise. B = *pink3. 6 coarse slang offens. = knock off 6. —n. 1 act or sound of knocking. 2 knocking sound in esp. An engine.  knock about (or around) colloq. 1 strike repeatedly; treat roughly. 2 a wander aimlessly or adventurously. B be present, esp. By chance (a cup knocking about somewhere). C (usu. Foll. By with) be associated socially. Knock back 1 slang eat or drink, esp. Quickly. 2 slang disconcert. Knock down 1 strike (esp. A person) to the ground. 2 demolish. 3 (usu. Foll.