It's defined pretty clearly as the overarching main play of your business, yet few managers can spell it out. In fact most CEOs get confused as well and just sprinkle the S-word as often as possible to sound important "going forward" (as if we can or want to "go backward"). It's strategy. And once it's out there, it gets overused. A tactic is a smaller play, one that (hopefully!) aligns with your overarching strategy, yet we see almost everything become a strategy and every division of our companies become strategic. Like strategic HR, strategic IT and strategic coffee-breaks.
I was prompted to write this because of this quote, from Harvard Business Press...In a nutshell, as illustrated below, mission is about what will be achieved; the value network is about with whom value will be created and captured; strategy is about how resources should be allocated to accomplish the mission in the context of the value network; and vision and incentives is about why people in the organization should feel motivated to perform at a high level. Together, the mission, network, strategy, and vision define the strategic direction for a business. They provide the what, who, how, and why necessary to powerfully align action in complex organizations.