Meanings of become dummy in English

As soon as Tracey became dummy, Flora suggested he go look for Sprague.

When Nita became dummy-

"Does anyone know the exact time Mrs. Selim left the room, when she became dummy?"

Ralph and I, Lois and Johnny were playing together, and just at the time I became dummy, Sprague became dummy at the other table.

"You'd just told me about Sprague's warning Karen not to leave the table when she became dummy after Judge Marshall's little slam bid in spades."