Lock is an ability name currently exclusive to Danger World and specifically to the Prison Dragon attribute. Lock can seriously stifle the opponent's offensive options and also prevents monsters from using [Move].
Latest Reminder Text
|"Lock" [Cost], choose X of your opponent's cards, and lock them. (Locked cards cannot attack or move to another area until the end of your opponent's turn.)|
List of Cards with Lock
Lock can be explained as the Prison Dragons capturing their enemies and sending them to prison.