Bull/bʊl/ Definition 1 of 5Pro Tip 1/2Gender Specific Use 'bull' only for male cows, not females which are called 'cows'. The farmer introduced the new bull to his herd. Pro Tip 2/2Animal Age 'Bull' usually refers to an adult male, while a young one is known as a 'bullock' or 'calf'. That bull started off as the strongest calf in the field.