mark someone's card

mark (one's) card

To alert one to pertinent information about something or someone; to tip one off. Shortly after I started, one of my coworkers marked my card about the boss's tendency to give very harsh criticism.See also: card, mark

mark someone's card

give someone information. informal This idiom, which dates from the mid 20th century, derives from the world of horse racing. The card is a race card , the list of runners at a race meeting, so to mark someone's card is to give them tips for possible winners.See also: card, mark