A pivot is when a company (usually a smaller company) decides that their current business model/idea isn't working, and "pivots" to another idea. Though to be fair, I arrived at this definition only by seeing it enough times on HN and defining it via context.
The word originally came from Eric Ries and the Lean Startup (I think). Pivot does indeed mean changing to another idea, though the emphasis is on "change direction with one foot on the ground", ie, not just scrapping everything to do something completely new. Though nowadays it seems pivot can mean everything from "slight change in direction" to "completely give up".
