Knocker

(n.) One who, or that which, knocks; specifically, an instrument, or kind of hammer, fastened to a door, to be used in seeking for admittance.

Thesaurus Entries

Thersites, backbiter, bag, belittler, boobs, bosom, breast, breasts, brisket, bust, calumniator, carper, caustic critic, caviler, chest, criticizer, crop, cynic, debunker, decrier, defamer, deflater, depreciator, derogator, detractor, disparager, dug, faultfinder, hatchet man, knockers, libeler, mama, mamelon, mamelonation, mammary gland, mammilla, mammillation, momus, muckraker, mudslinger, nenes, nipple, pap, papilla, pigeon breast, railer, slanderer, smellfungus, social critic, teat, thorax, tit, tits, titties, titty, traducer, udder