Hall costumes are costumes some attendess at Worldcons and other conventions wear in the hallways and around the con, rather than only at the formal, judged masquerade. Some conventions even provide judging for hall costuming.
Hall costumes actually predate the concept of a costume party or regular masquerade. The first time sf fans wore them at a convention was in 1939 when Morojo designed and created "futuristicostumes" that she and Forry Ackerman wore to Nycon 1.
Hall costumes may be elaborate or simple, ranging from complete full-body covering and detailed outfits from the wearer's favorite sf or fantasy world to just a few accessories. "They glue a gear on it and call it steampunk," Dick Smith has scoffed.
Sometimes it's hard to tell whether some fans clothes are meant to be cosplay or merely their idiosyncratic way of dressing. During the 1970s, for example, it became a trend for fans in the Midwest and mid-South to wear caftans to cons (after a group of browsing fen discovered a big sale on them in the hotel gift shop at Rivercon). Stfnal t-shirts and shirts denoting cons and clubs are popular, too. (in the 1950s, CFG members sported matching bowling shirts.)
Contributors: Dr. Gafia. others.