Variable Nozzle Turbine. Garrett's name for their variable-geometry turbine, which uses vanes in the inlet section of the exhaust turbine to keep the gas speed up at low revs and extend the range over which the turbocharger can deliver useful boost. It's a much better way than wastegates, as it works over a wider range and doesn't throw energy away. VNT turbines have no wastegate, the vanes do all the boost control.