Yellow-card is a term used in sports to indicate a warning to a player for an infraction of the rules. It is usually shown by a referee or umpire holding up a yellow card, which signals that the player has been warned and any further infractions may result in a red card and ejection from the game. The crossword solutions for the term YELLOW-CARD are WARN, which is an appropriate word to describe the action of the referee or umpire.