Japanese, literally translated to "thin hammer". can be taken as being called useless. But in the context of the Naruto universe, it takes on a sexual meaning. so, not useless. but an insult to ones penis
Guy A- usuratonkachi
Guy B- What in the hell did u just say?
Guy A- I just said you had a thin hammer
Boys who enjoy yaoi (a genre in Japan that contains sexual and/or romantic relations between two men); literally translates to "rotten boy"; corresponding female : fujoshi