Students need to think and work across disciplinary boundaries in the 21st century. However, it is unclear what interdisciplinary thinking means and how to assess students' interdisciplinary understanding. In this paper, drawing from multiple perspectives in the learning sciences, we aim to apply and refine a theoretical framework that helps define interdisciplinary learning in science. Specifically, we examine four cognitive dimensions of interdisciplinary understanding: integration, translation, transfer, and transformation (IT3 framework). We apply the framework in analyzing the conversations among university faculty members from different science disciplines who strive to improve college level science education. We report our results and further discuss the implications of using our framework in conceptualizing interdisciplinary learning.