PLONKER Meaning of PLONKER in English ■ noun Brit.1》 informal a foolish or inept person. 2》 vulgar slang a man's penis.OriginC19 (as a dialect word meaning 'something large of its kind'): from plonk 1 + -er 1 . Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004