an eppo is someone who is really, REALLY dumb and stupid as hell. Not someone that has just a few dumb sayings, but someone of which you think: 'how can you be só dumb. This isn't possible. Supernatural maybe?'
Ben: Look! that's the big ben!
Ed: It's the Statue of Liberty, you eppo.
A slang word from Dublin technically meaning to an epileptic fit. Its more likely to mean you over-reacted to something. You can have or throw an eppo. It was very popular around the time of the movie My Left Foot.
"Jacinta had an absolute eppo when she heard that Saoirse was texting yer wan"