This paper examines how hearing impaired students defined prism and used gestures in the process of this defining. It was utilized fenomenology of qualitative research methods. Opinions of two hard-hearing students' were consulted. It was used the grounded theory tecniques to analyze the data. Results indicated that the students used iconic, metaphoric, deictic and ideographic gestures and sign language, besides the gesture, engaging in mathematics, explained prism as an object which had base, surface and height. It has been found that students have either missing or incorrect information about prisms. Because of the students used the hand movements, it can be suggested that teachers should use hand, arm and body movements in the process of embodying concepts in classroom practices in the present study. [Part of this study was presented as an oral presentation at the International Conference on Research in Education and Science (ICRES) May 19-22, 2016.]