Refers to a Maori male (also manly Maori females), usually said in a Maori accent. Derived from the belief that shouting 'D' is the tribal calling of the Maori language.
Only saying 'D!' is commonly used as well. (Also said in a Maori accent)
Look at that Hey-D over there. (Hey-D is said in a Maori accent whilst the rest is said in a normal accent)
That group of Hey-D's over there look scary, we should avoid them.