Colloquial use: "We were working on an enterprise database solution, then pivoted to a social network for toddlers."
Intended use: "We were working on a time tracking application for freelance designers, and pivoted to making it for lawyers instead."
There are lots of kinds of pivots (customer segment, platform, channel, value capture, engine of growth etc) - in essence, it's about taking what you've learned so far, and using that knowledge to tweak your approach to solving the problem you're working on.
Eric Ries' 'The Lean Startup' is the canonical reference for this stuff.
