A blank is a playing card in card-point games that is a non-counter, or is worth nothing.
[1] In Poker, the term refers to a community card which is extremely unlikely to help any remaining player.
In the German games of Schafkopf, Doppelkopf, Sixty-six and Skat, the 7s, 8s and 9s in all card suits are Luschen.
In Bruus and other members of the family they are 'duds' (Luschen or Fosen) or 'worthless cards' (wertlose Karten), but in Brus they are called 'windmills'.
In Bräus, they are literally unplayable and only serve to pad out the hand.