noun. Someone on the extreme edge of whatever their -ism happens to be.
(coined by Perry de Havilland)
Usage:"Definition of a 'barking moonbat': someone who sacrifices sanity for the sake of consistency"
The term (often rendered simply as 'Moonbat') is very popular with conservative and libertarian bloggers who appropriately use it to describe the Chomskyite Left. (also see 'idiotarian').
Note: Contrary to some speculation and entries on Wikipedia, Perry de Havilland has stated it was was not originally a play on the last name of George Monbiot, a columnist for The Guardian, as he was using the term long before he met or had even heard of Mr. Monbiot.