A ball is "in play" as soon as the player has make a stroke on the teeing ground. It remains in play as his ball until holed out, except when it is out of bounds, lost, or lifted, or another ball is substituted in accordance with the rules.
Cards that have been played and are still on the table. Your deck and your discard pile are not in play.
of a ball; "the ball is still in play"
A card that has been placed on the board is considered in play. (Exception: cards in cadre or the dead pile are not "in play.")
Within the course (not out of bounds).
Your cards on the table are considered to be in play. Basic Pokémon, Evolution cards, and Energy cards can't be used unless they are in play. (The cards in your deck, your discard pile, and your Prizes are not considered to be in play, but your Benched Pokémon are.)
when a ball is within the boundaries of the field and play has not been stopped by the referee.
The ball is in play as soon as the player has made a stroke in the teeing ground. It remains in play until the player has holed out, except when it goes out of bounds, is lost, is lifted, or is replaced by another ball in accordance with the rules.