This poker term means almost the same thing with the term "action." It stands for tell a player that it's time for them to act. To carry out an act when it is your time to do that. Some of the common terms associated with the "act" term are call, fold, check, raise and open bet which are all terms showing a call to action. To do or let another player do, or still go ahead with the other players to perform an action all define the term "act."
There are times when a player has to act as part of the rules of the game. A dealer is always mindful of what the players at doing every step on the way; so part of his duty is to call them to order. Such wake up calls are part of the "act" where players are often told politely to do something that will keep the game in play. There are several expressions for action such as "Let's go elsewhere to get some action."