Baka desu

baka desu, excl, foreign ("bah kah dess"): 1. Japanese: "It's/that's/you're stupid!"; baka "foolishness" desu "to be" 2. Gamerese: "It's/that's/you're stupid!" From anime. Also baka, darling no baka. [GJ1]
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Addendum: For full effect, the word "baka" should be pronounced with an extremely long first "a," in imitation of anime characters; "baaaaAAAAAaaaaka desu!" [GJ1]