A complete change of direction or opinion.
The friendly welcome was a 180 from what she had been expecting
The exact opposite.
An instance of spinning 180 degrees, so that one is facing in the opposite direction.
An abrupt change of opinion.
An automobile driving manoeuvre where the driver starts turning the vehicle and then pulls on the handbrake to make the rear tyres lose adhesion and thus cause the back of the vehicle to slide around (in the direction of the turn).