What exactly is a sword bomb?

Also, One Piece is an Anime about pirates in which the main character is rubbery - thus (I think) you can stretch him and he is invincible to blades and sharp things like that. The only "ability" that caught my attention is that he can stuff himself in a barrel. Well, that's all I got from watching 10 mins of the first episode - Totally Spies was on another channel. But yeah, it is more of slapstick comedy.