Merriam-Webster Collegiate Dictionary - costume

 I. noun  Etymology: French, from Italian, custom, dress, from Latin consuetudin-, consuetudo custom — more at custom  Date: 1799  1. the prevailing fashion in coiffure, jewelry, and apparel of a period, country, or class  2. an outfit worn to create the appearance characteristic of a particular period, person, place, or thing Halloween ~s  3. a person's ensemble of outer garments; especially a woman's ensemble of dress with coat or jacket  • ~y adjective  II. transitive verb  (~d; costuming)  Date: 1823  1. to provide with a ~  2. to design ~s for ~ a play  III. adjective  Date: 1847  1. characterized by the use of ~s a ~ ball a ~ drama  2. suitable for or enhancing the effect of a particular ~ a ~ handbag