ANBU (暗部, literally "dark side") stands for Ansatsu Senjutsu Tokushu Butai (暗殺戦術特殊部隊). Translated into English, it roughly means "Special Assassination and Tactical Squad". The name is a play on words, as in English acronyms like S.W.A.T. or S.H.I.E.L.D., where the two kanji used to abbreviate the group's full name constitute an actual word on their own.
ANBU, known in the Viz manga translation as "Black Ops", is a force of extremely talented shinobi who perform assassinations, protect the village from exceptional threats, conduct high-risk missions into enemy countries, and deal with extremely strong (S-Rank) ninja. They wear animal masks, speculated to be used in order to distinguish themselves from normal shinobi or to conceal their identities. Unique for most characters in Naruto, all ANBU appear to carry swords, or Ninjaken. The ANBU is an organization that serves under the direct command of their Kage.
If you want to be ANBU, post an RP sample here. If there are multiple posts, then the best will become Head ANBU.
