Railbird
Also: rail, on the rail, sweating
A spectator watching a game from outside it — from the rail that separates the playing area from the rest of the room. The word covers everyone from a busted player waiting for a friend to the crowd around a high-stakes table.
Rails matter more than they look. Most rooms forbid a railbird from discussing a live hand with a seated player, since that is a route to collusion, and tournaments restrict who may approach a table at all. Online the equivalent is the observer list on a table, and the same concern applies: a watcher relaying information to a player is cheating, and it has a name of its own.
'Sweating' a friend from the rail is the accepted version, done between hands and without comment on live action.
Related terms
Full glossaryFrequently asked questions
Can a railbird talk to a player during a hand?
No. Almost every card room forbids it, because passing information to a live player is a form of collusion.