Plonker

[Monty]

A foolish or inept person.

[Jason Yan]

dope, idiot, moron, wally, [pillock], [dunderhead], [dimwit]

[Zipporah Schumaker]

the term plonker started out as a reference to someone who was forever drunk on [cheap wine] (cheap wine is nicknamed [plonk]) this person was usualy a homeless person, or poor person.

today the term plonker is a very light hearted insult. Its not even seen as an insult, its like calling someone [a wally]. Its in no way ment maliciously. you call someone a plonker when they say or do something stupid.

[Magaret]

[a willy]! or a [dopey] [person]

[Tanya Shivari]

[someone] [stupid].

[Lanell]

[A stupid] [person]
[A penis]

[Marquetta]

a poo that is so heavy that makes a massive splash with the [toilet water] [that hits] [your arse] and makes you feel wet.

[Justin Bieber]

Almost any penis, but not a very small one.
A foolish person.
A [big wet] kiss.
Almost anything that is remarkably big.

Almost certainly most derive from plonker as size, but this in turn possibly from to [plonk], to place with little or no accuracy possibly because it was big and heavy. See also [plonka].

[Donald Trump]

A polite, in [mixed company], and alternative word for [stupid cunt] and [wanker].

[Agnes]

To be [so drunk] youre [unable] to [remember] the meaning of certain words.

[Sarah]

a silly or stupid person: