FSSJ

False Super Saiyan (疑似超サイヤ人, 'Giji Sūpā Saiya-jin')-Saiyan Transformation, That was used by Goku during his battle with Lord Slug in the movie Dragon Ball Z: Lord Slug, It appears that only Goku was able to use this transformation. During the film King Kai stated that this was the Super Saiyan transformation but was re-labled to be "false" after the manga revealed the true Super Saiyan Transformation