Early '90s UK slang, said to someone slow on the uptake. Comes from a TV advert. Used in the same context as Duuuuh! or McFly! Example: Hey, why are you wearing your coat? Are you going outside? Dime bar!
DIME BAR!
Meaning of DIME BAR! in English
Slang English vocab. Английский сленговый словарь. 2012