In this paper, we report findings from a larger study that investigated design failure, as a phenomenon, in instructional design (ID) practice from the perspective of ID practitioners. Following an interpretive phenomenological study design, we interviewed 17 ID practitioners working in diverse settings, seeking their stories of design failure. Throughout the interviews and the analysis of the practitioners' stories of design failures, we found that ID practitioners define design failure in different ways that are mostly not captured in design literature, that is: design failure as "failure during use of design," design failure as "failure during process of design," design failure as "an opportunity for reflection on design actions," design failure as "an outcome or an event that needs to be avoided/prevented during the process of design," and design failure as "an outcome or an event that could not be avoided/prevented during the process of design." These findings and our discussions of them emphasize the generative role design failure plays in ID practice, the richness and the complexity of this phenomenon, and point to implications for IDT scholarship and ID education. In an upcoming paper, we report what ID practitioners attribute design failure to and what is the essence of design failure in ID practice.