Sometimes, due to limitations in the search procedure and the size of the online dictionary, particular words cannot be found in the current version of HyperDic.
You can eventually try alternative spellings, or look in HyperDic's Alphabetical Word Index. Please note that HyperDic only knows generic word forms. More information about word lookup is available in the Search Help.
More comprehensive English web dictionaries might have more knowledge about a word you want to look up. The following, freely accessible online dictionary sites, cover extensive portions of the English vocabulary: