The Delayed trigger is always accompanied by a number. The number specifies how many turns must end (not including the turn the card is played) before the trigger then activates at the start of the next player's turn.
For example, a Delayed 1 trigger will activate at the start of the player's turn after the zombie is played. After playing a zombie with a Delayed 2 trigger, the player will end their turn and then take one more turn before the trigger activates on the enemy's turn after that.
List of cards using this keyword
See the delayed category