Japanese, best translation comes out to "soul cutter." Supernatural weapons used by shinigami in the popular Bleach manga/anime. Each zanpakutou has its own power and persona. Zanpakutou purify Hollows and send spirits to Soul Society. Although, they're also kickass weapons that have two forms of attack (releases). There's the shikai and the strongest, bankai, which can do anything from crate a giant-ass monster thing to giving you a badass yakuza look :p
Did you see Renji use his zanpakutou's bankai?! It was sweet!