A pivot could be characterised as an assumption that is proven wrong where change, sometimes drastic, is needed.
A pivot is not necessarily drastic.
Pivot examples
Changing sale channels Targeting a different customer group Changing core features
Reference
Ries, Eric. The Lean Startup: How Today’s Entrepreneurs Use Continuous Innovation to Create Radically Successful Businesses. 1st ed, Crown Business, 2011.
Highlights or timestamps
A main characteristic of a pivot is that the core assumptions behind the startup have changed
— ^a82e65 from The Lean Startup