In Jamaica it means large hard penis. Woody. The big bamboo.
Steve bought a "jamaican guitar" that was made out of a large piece of bamboo. "Big bamboo" was painted on it. Steve thought it really was a jamaican musical instrument. It was not. It was the Big Bamboo! Made by the locals and sold to stupid tourists who didn't realize they were really purchasing a big penis! (Hey, mon! You see that stupid tourist spent $20 on the big bamboo!)