In Japanese, the word ばか baka means "idiot", "moron", "fool" or "dimwit". It can also refer to the condition of being stupid. The word is widely used in conversation and, while derogatory, is not taboo. It is more commonly used in Tokyo and other parts of eastern Japan while in Osaka and elsewhere in western Japan, aho is the usual preferred equivalent.
When used as an adjective in Japanese, baka (na) can mean "absurd" or "crazy" in addition to "idiotic." The adverb form baka ni can mean "extremely" and baka ni dekai "extremely large". Baka ni naru can also mean "overdo" or "overwork".
My brother knows some japanese since he loaned a book in a library..it was murder to listen to him speak it without understanding ^^