Kirby: A derogatory term for an annoying women from Australia New Zealand or South Africa. A Kirby would typically be blonde (or dyed blonde), slightly slutty and fond of her alcohol and/or drugs.
This word originates form a short lived UK TV show called The Last Chancers which featured a character called Kirby who was as described above.
Note on usage: This word could be considered very offensive as it shows a complete ignorance of the difference between three very different counties. Bare in mind that Kirbies are often in the company of large, blonde, rugby playing men whom you may not want to upset, especially after they have had a few.
Credit to greatest_fay for bringing this word into more common use.