adj: Used in Edinbourgeois slang, often as a comeback.
When something (especially someone or something being said) has gone too far, is over-the-top, or silly; but still in a jokey way.
When said about something that's been said it is usually followed by "from you".
Alex says "Jane, You have a massive forehead, it makes you look like a donkey."
Betty says "Mate, Plenty from you."
After seeing something silly, Charlie exclaims "That's Plenty"