Derogatory word. Comes from a mixture of pleb and flange. Used to describe someone who acts in a stupid way, but sometimes used as a friendly joke.
Oi, Tom! You little plenge!
That geezer's a right plenge.
You bloody plenge!
Another word to describe a womans 'front bottom'
'Don't bother with her, she's got a plenge like a fish market' or from an admiring partner 'wow hunny, you waxed your plenge!'