The term BASEBALL UNIFORM PART can be solved with the 3-letter answer CAP. A baseball CAP is a type of soft hat with a rounded crown and a stiff bill projecting in front. It is typically made of cloth, and often has a button on top and a small brim in the front. Baseball caps are popular among both men and women and are often used as a fashion accessory. They are also worn by athletes to protect their eyes from the sun and to keep their hair out of their face while playing.