A better, more correct version of 'dunda head.' Dunder brain can be used as a friendly insult, but do not try actually paying somebody out with this word, because you will seem like a complete moron, and a 'dunder brain' yourself.

Can refer to someone who is muddled in the brain, or a generally silly person.

the art of remembering an arousing occurrence or some porn you watched while masturbating, often handy if you have no porn or your in the shower