A further bastardisation of the word "pure" by scousers.

The word you say when you have to pee but you're excited at the same time. Pyay!

a colloquiaism from Liverpol that replaces 'very' or 'really'. It has evolved from Liverpudlians using the slang term 'pure' to mean the same thing, it then morphed to become pyar and then pyay.