We present a hybrid text mining method for finding abbreviations and their definitions in free format texts. To deal with the problem, this method employs pattern-based abbreviation rules in addition to text markers and cue words. The pattern-based rules describe how abbreviations are formed from definitions. Rules can be generated automatically and/or manually and can be augmented when the system processes new documents. The proposed method has the advantages of high accuracy, high flexibility, wide coverage, and fast recognition.