It's just an expletive that expresses light disapproval about something that someone's saying. Mr X: "I'm going to the club Fabric tomorrow night" Mrs Y: "Bleurgh! It's such a rip off and Embassy is way better!". OR: Mr X: "Sorry but I really can't talk now, I've got way too much to do." Mrs Y: "Bleurgh! You never make time for me anymore". It's just a light-hearted expression for disapproval :). Take care!