Definition of door card
The door card is, in Stud, a player's first open card. It is the term used by Stud players to describe a player's visible card on 3rd Street (the first round of betting). In a Stud hand, players are dealt 3 cards. Two of these cards are hidden and one of these cards is visible to all players at the table. This is quite different from Hold'em where the players' private cards are hidden.
Some notions of Stud in relation to the door card
This visible card will give the other players an idea of the strength of a player's hand, and from this information they can assess their future actions. The face-up card can be referred to as the "door card" or simply "door". Although "door" translates to "door" in French, there is no real French equivalent that is used regularly. In many parts of Stud, even among French speakers, the door card will be used. The door card also has another use; it will determine who will play first on third street. The player with the lowest card will play first.