The use of design as a critical tool to explore design's potential roles in society and the future has emerged as a trend in HCI and design research, but several questions remain open. How can we explain and teach how criticality can be applied to design? How can we assess, compare and give context to critical designs? How should we understand the relationships among practices that bear affinities to critical design, such as speculative design or critical engineering? We argue that many of these issues would be clarified if the HCI and design research communities had a collection of examples that exemplified not just critical design in general, but also its major genres, styles, historical trends, rhetorics, and other distinctions. As a first step in this direction, we detail our efforts to develop a more systematic vocabulary to talk about critical design. After assembling a small operative corpus from a wider inventory of critical designs, we apply poststructuralist semiotic theory to propose a number of analytic distinctions and concepts that could be used-along with others like them- to more systematically and deliberately construct a canon of exemplars and a more mature conceptual vocabulary for critical design.