As a Noun: 1. For deaf or hearing impaired people, the speech of a hearing person which is impossible to follow through listening or lip reading. 2. Language (speech or signed) that does not make any sense. English = gibberish. 3. A concept or proposition that is not clear. As a Verb or Adjective: 1. To have not the slightest idea of what something means, especially when you think that no one else would understand either because the information is confused or incomprehensible. 2. Of deaf or hearing impaired people, to be completely unable to follow someone's speech (either through listening or lip reading). 3. To be so surprised at something that you have no idea what to say. English = (be) speechless, (be) dumbfounded. Interactive: 1. Used alone to tell your addressee you do not understand what they mean or what they have said, or that you are puzzled. 2. Used alone in response to a question to mean you do not have the slightest idea what the correct answer is (and you don't much care either!).