1. A method for context-based disambiguation of abbreviations, comprising: determining a target abbreviation and one or more keywords appearing in context with the target abbreviation in a received passage, the target abbreviation representing a shortened form of one or more words; generating automatically by a processor, a contextual search query comprising the target abbreviation and said one or more keywords; searching, by the processor, a pseudo document index for one or more expansions of the target abbreviation by invoking the contextual search query, the pseudo document index containing index of one or more pseudo documents by titles, associated one or more abbreviations, and associated context keywords, wherein the titles are the expansions of the abbreviations contained in the pseudo documents respectively; returning one or more target pseudo documents associated with the target abbreviation based on the searching of the pseudo document index; and providing one or more expansions associated with the target abbreviation based on the returned one or more target pseudo documents, wherein the determining the target abbreviation and one or more keywords appearing in context with the target abbreviation in a received passage comprises generating one or more features that capture lexical and syntactic properties of the passage, and recognizing said target abbreviation and said one or more keywords appearing in context with the target abbreviation in the received passage based on the captured lexical and syntactic properties.