Abstract: In this study, a novel feature selection framework was proposed for extracting definition from aviation professional corpus. The framework combined between-class and within-class distribution difference to express contribution of small disjuncts in classification and increase precision and efficiency of definition extraction. In this study, definition of the framework was introduced and influence of feature selection made by the framework and traditional methods was compared. Results using traditional methods and the proposed framework in different classification strategy were contrasted in the end. The results indicated that the framework introduced in this paper is better than traditional methods in extraction definitions.