A mildly stereotypical 'gangsta' greeting. Used more often by white boys.
Best pronounced "Boooooooooooooooom" followed by an Ali G-esque finger snap.
Can also replace the phrases "I emphatically agree" or "Thats the bestnews I heard for ages"
"Booooooooooom"
"Word"
Or
"Mate, I've just won the lottery"
"Booooooooooooooom"