Like a piss up however a much nicer word. Normally involving drinking lots of beer.

An irresistable urge in your bowls causing you to run to the shitter after drinking a hot cup of java at work.

From world war two and used, usually by British soldiers, to describe the effect seen when the amunition propellant in a destroyed tank starts to ignite. The flames shoot out of any opening, most usually the turret hatches, extremely violently, like a Roman candle. This terrified tankers and as a sort of black humour they referred to it as brewing up.

Other nationalities sometimes referred to it as cooking off .. the ammunition was cooking off.

Slang for masturbating

1) Brew - Substitute for any verb
2) It - Substitute for any noun
3) Up - substitute for any verb

To make a pot of tea. Usually used in the context of plural .. a pot of tea of several cups, rather than single cup, when you would instead say, "making a brew"