Term used to describe one of the famous Gibb brothers, often said in excitment/shock when actually seeing one in the street. The extent of the shocked exclamation is often higher if it's Maurice Gibb who is spotted.
Look there's a real life Bee Gee! (as heard on Only Fools and Horses 'Miami twice' episode)
I saw a Bee Gee down the pub the other day and he was talking about miami while stroking his hair.