Abstract“Social movement unionism” (SMU) is frequently understood as the antithesis to business unionism. While business unionism, often characterized as bureaucratic and hierarchical, dominated most of the second half of the 20th century, “SMU” showed resurgence in the 1990s. Some scholars argue that SMU should reach beyond the workplace and incorporate the community. Others seem to be proposing a strategy and understand SMU as tactically innovative and mobilizing in alliance with traditional social movements, such as the women’s, environmental, or immigrant rights movement. Some offer propositions about the social processes of a labor union and that SMU must be internally democratic. Finally, some advocate an internationalist component such as a link to global‐justice campaigns. In this article, I propose that SMU consists of an array of trends and is inclusive of these varied descriptions, strategies or processes. These trends include (1) rank‐and‐file mobilization, (2) leadership, (3) community‐based organizing, (4) worker centers, (5) corporate campaigns, and (6) transnational components. I draw on social movement and labor literatures to seek a broader understanding of this labor organizing form.