Colt/kəʊlt/ Definition 1 of 4Pro Tip 1/3Age Specific The term 'colt' usually refers to a young horse under four years old. When the colt turns four, he'll be trained for racing. Pro Tip 2/3Gender Specific A colt is specifically a young male horse; females are called 'fillies'. Look at that colt playing; maybe he will race alongside his sire one day! Pro Tip 3/3Potential Misuse Don't use 'colt' for adult horses; it's a common mistake among learners. He's not a colt anymore; he's grown into a fine stallion.