Costume/ˈkɑːstuːm/ Definition 1 of 3Pro Tip 1/3Character Role Used when dressing up as someone else, often for fun or a special event. I need a pirate costume for the school play. Pro Tip 2/3Special Occasions Typically worn for celebrations like Halloween or themed parties. Everyone had creative costumes at the masquerade ball. Pro Tip 3/3Not Everyday Wear A costume is not for daily attire; it's for specific roles or events. You wouldn't wear a superhero costume to the office.