This is a term given to people who are often abnormally tall and will, without question, eat anything. This can be anything from leftovers to jars of brine.
They have a strange tendency to wear sunglasses indoors in a futile attempt to cover up the damage of the previous evening, often spent with short chavs.
The sister term, 'bellend', which summarises the above, is sometimes used when time is of the essence, or to finish off a sentence which already includes the term, Big Fat Wanker Dyke
"Look at that Big Fat Wanker Dyke eating everyone's leftovers and drinking that brine from the finished olive jar, what a total bellend."
"I know. It's a good job she's wearing her sun glasses indoors though, otherwise she'd look proper hanging. No doubt was with that short chav again!"