The true definition of the word refers to the popular disc-shaped toy that can be thrown around by machoegotists on the beach. However, it can also refer to any old videogame on CD that you no longer want and is so old, it's impossible to sell. Even on Ebay.
"God damn, I've sure got a lot of frisbees here. You want some?"
Similar to a bilbo, a pidgeon was a character during games of AD&D who wasn't given much chance of survival. What seperated a bilbo from a pidgeon was not bad luck but a staggeringly poor performance during combat. Custom dictates that other players must coo repeatedly when a pidgeon is trying to attack someone.
"Don't worry about Tharg The Destroyer, he's a real pidgeon..."
For whatever reason, a bilbo became the name given to an individual who wasn't given much chance of survival during games of Advanced Dungeons & Dragons. For added humililation, the name was pronounced in a low voice with the emphasis on the O. Also used to designate an NPC who was clearly about to die in a poorly disguised plot twist.
"Oi, Bilbo! Just pop your head around that door and tell us if any orcs are there... oh, he's been shot in the head."