Someone who pontificates about subjects
(especially science, especially climate change) in the pub (or, even
more likely, the golf club), while
having no idea what they're on about. Typically
to be found drinking gin and tonic, wearing a blazer, calling people "squire", playing golf, and driving a Jaaaaaaag.
"All this global warming
nonsense. The Romans grew grapes in Yorkshire! Explain that!"
"You're right, Ken. Several thousand climatologists and many petabytes
of hard evidence
can't stand up to a single well-informed gintellectual."