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2.
Rainbow formal is a dress code similar to black tie, where the attendees to the event (normally a ball or awards ceremony) are required to not wear the usual white shirt, with black tie, jacket and trousers and instead wear more colourful attire.
"We organised an event and eschewed the usual black tie formal and went for Rainbow Formal"
by Ben Whitehouse May 02, 2006
 
1.
Rainbow formal is a dress code similar to black tie, where the attendees to the event (normally a ball or awards ceremony) are required to not wear the usual white shirt, with black tie, jacket and trousers and instead dress like a idiot in their stupid coloured jackets and shirts, while still trying to stop people turning up in jeans and a t shirt, or anything that doesn't look stupid.
"we organised an event and eschewed the usual black tie, instead choosing to dress like a bunch of tosspots in 'rainbow formal', while remaining smug and snobby by avoiding casual dress."
by a sensible person March 21, 2007