This paper describes a method for extracting disambiguated (bilingual) is-a relationships from parallel (English and Japanese) dictionary definitions by using word-level alignment. Definitions have a specific pattern, namely, a "genus term and differentia" structure; therefore, bilingual genus terms can be extracted by using bilingual pattern matching. For the alignment of words in the genus terms, a dynamic programming framework for sentence-level alignment proposed by Gale et al. [6] is used.