Reflection is fundamental in experiential pedagogies, and many studies have been carried out to investigate its impact and benefits on student learning outcomes. However, the concept of reflection is not well understood. In this study, we focus on the concept of reflection and ensuing approaches to it in service-learning, an experiential pedagogy that has been hailed as a high-impact practice in higher education. We first survey the semantic background of reflection and its usage in service-learning literature. We then present a qualitative study of how university faculty involved in service-learning actually conceive reflection. In-depth interviews uncovered common tendencies as well as concerns about handling reflection in service-learning courses. We devised a framework to map teachers' conception of reflection onto the service-learning goal of transformative education. From the data set, we identify four conceptual domains echoing varying conceptions of reflection in literature: reflection as "transformative learning," as "mindful practice," as "evaluation exercise," and as "articulated thinking" -- with the most popular being evaluation exercise and transformational learning.