Only the absolute most gangsta sport in the entire world. Duh.
Basicly, climbing to the top of big rocks. Really big rocks are called highballs. And you don't climb a boulder; you "send" it.
The great thing about it is that all you need is a chalkbag(Prefarably filled), climbing shoes and a crash pad. If you're thrifty all under $200 bucks--and they last forever.
Dude, this weekend I'm going bouldering on that highball that you couldn't send.