“Build” simply means having something that you can test with customers, which could be a live product or design artifacts, such as wireframes or mockups. “Design something to test” is a broader, more accurate description, so I prefer the label “design” for this step. The goal is to identify and create what will let you test your hypotheses while consuming the least resources. “Measure” implies numerical data—but keep in mind that “measure” doesn't have to be as quantitative as it sounds.
