Nimbrain 

Another word for idiot or a weirdo or someone that has done something silly.

'Your such an nimbrain sometimes!'

Nimbrain by KC&GD February 21, 2012

Nimbrain 

Someone who says/does something or is stupid.

A polite was of saying Retard or Dickhead etc.

Kathryn: I'm so much cooler than you!

George: Oh dear, you really are a nimbrain!

Nimbrain by supercoolguy April 9, 2012

Nimbrain 

A polite way of calling someone an Idiot.

Girl: I'm so much cooler than you!

Guy: Oh, you really are a Nimbrain!

Nimbrain by thecoolestguyintheworld April 12, 2012