That is a remarkably slippy statement.
Just prior to the restart, there was a short rain shower which made the track slightly slippy.
One of the more frequently mentioned ones, for example, was slippy-slidey ice worlds - levels in platform games with slippery, ice-covered floors, thus making progress haphazard.
For example, a gloss surface can be too shiny to the eye and too slippy to the finger (a touchpad is a good example) so a controlled roughness is required.
