box jumper
n.— «I hate enclosed spaces, which people find amazing because in illusions I’m pushing other people into boxes or tight little spaces. People who get into those contraptions are called box jumpers and that’s something that I could never do—because of my phobia and my size. Box jumpers need to be very thin and agile.» —“Interview: Paul McEneaney—The Magic Of It” by Gail Walker Belfast Telegraph (Northern Ireland) May 5, 2007. (source: Double-Tongued Dictionary)