Flase Super Saiyan is a transformation used by Goku in movie 4 Dragon Ball Z: Lord Slug.
It is obtained when the Saiyan has the required physical power but lacks the required mental strife to transform into a Super Saiyan. It was intended to be the release of super saiyan.
The aura of the False Super Saiyan is similar to the aura of the Kaio-Ken technique. Later in the making of Lord Slug false super saiyan was to become a heightened form or Kaio-Ken when the aura changes cover this mistake.