1. A method for updating a dictionary in a dictionary updating system with an unregistered word not registered in the dictionary, the method comprising: extracting a document of interest of a user in each predetermined extraction period from a predetermined server connected to the dictionary updating system through a network, and extracting candidate unregistered words existing in the extracted document according to predetermined unregistered word extraction rules; extracting unregistered words among the candidate unregistered words and extracting candidate semantic classes of the unregistered word based on information on appearance frequencies of the candidate unregistered words retrieved from the document; verifying the unregistered word according to a predetermined unregistered word verification method and determining the semantic class of the verified unregistered word with usage examples of the unregistered word obtained through a searching unit; and updating the dictionary updating system with the verified unregistered word and the semantic class of the verified unregistered word.