Boardlock

From Poker Wiki

Boardlock is used mostly in Razz, where you are able to see so much of your opponents hand you can tell if they are drawing dead.

Everyone has to use at least two of the four face-up cards in their hand to make a final five-card hand. If they have 8-9-Q-7 showing, the best hand they can make will have a 9 as the highest card. They are "boardlocked to a 9." In this example, they are boardlocked to a 98, so 9832A is the best hand they can have. Any hand less than a 98, will win.