In education, professional development (PD) is the continuing education of teachers and administrators. Many studies have described PD as a conventional, top-down type of training that teachers experience in schools. Commonly known as the "institutional model," this type of PD is isolated from classroom practice and occurs as mandatory workshops, courses, seminars, and brief trainings by experts. Researchers argue that institutionalized one-day models of PD are often not applicable to teachers' needs, do not have any follow-up, and are expensive. Researchers have pointed to a lack of clarity and consensus about the meaning of PD, and much of the research focuses on building a common conceptual framework for researchers to understand and better measure the construct. Such research has provided insight into the fragmented nature of PD; however, it has not provided a deeper understanding of how teachers perceive and describe their PD experiences and what teachers deem as best for themselves and their students. Thus, the purpose of this study is to describe and explain three Title I high school teachers' experiences of PD, while capturing their perceptions of the meaning of PD. This study suggests that PD--as defined by the participants' experiences--is a nested construct differing in meaning depending on top-down mandates, and formal and informal opportunities to learn at the school, district, and individual teacher levels. Based on the participants' descriptions, effective PD is directly linked with increases in student learning. Further investigation of teachers' actual PD experiences, disaggregated at multiple levels, is needed to empirically document PD and to account for how teachers understand and hold themselves accountable for their own professional learning process to become "better" teachers.