Not British slang...it is from the 90's TV show "Newsradio". Secretary Beth decides to make up a word and see if she can get others to use it by dropping into every conversation. By the end of the day, everyone is using it. Has become popular in Britain due tothe popularity of the show.

It means to flip out or go a bit nuts, or to rant about something.
Beth went completely bitchcakes when she found out Matthew told Joe they were sleeping together.

Katherine is going to go bitchcakes on Bill after hearing that news story.
by BlooPenguin March 27, 2007
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bitchcakes British slang term meaning to go crazy with anger.
I wanted to go bitchcakes at my teacher for failing me on purpose!
by Jade Skellington December 28, 2005
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