A racecard is a list of the horse races that will happen at a meeting that day, and of the horses that will run in each race. You often buy a paper one at the gate. It usually also gives the extra facts people who bet like to read: the horse’s recent form, the rider, the number, the weight. Though actually many people now look at the same information on a phone; the paper card is the old way, and still common at the course. It is a horse-racing word, mainly British, not a playing card and not a number pinned to a runner’s shirt.