This form was originally labeled as the true Super Saiyan form, but later re-labeled as "Giji" or "Pseudo" Super Saiyan after the actual Super Saiyan form was introduced in the Dragon Ball manga.
In this form, a Saiyan's irises and pupils are no longer visible. His body bulks up a little, his hair almost straightens, his skin color also appears to have a yellow hue to it, but there is no considerable change in feature other than a red tint to his hair (due to the reflection of the yellow aura on his hair, his hair is not actually red). He gains a yellowish surge of aura.
One way to put it is that the Pseudo Super Saiyan transformation occurs when a Saiyan doesn't have a strong enough mental urge to properly transform. It is apparent, however, that the form gives a large power increase, enough for Goku, who was being easily beaten previously by Lord Slug, to now quickly overwhelm him.
In this form, a Saiyan's irises and pupils are no longer visible. His body bulks up a little, his hair almost straightens, his skin color also appears to have a yellow hue to it, but there is no considerable change in feature other than a red tint to his hair (due to the reflection of the yellow aura on his hair, his hair is not actually red). He gains a yellowish surge of aura.
One way to put it is that the Pseudo Super Saiyan transformation occurs when a Saiyan doesn't have a strong enough mental urge to properly transform. It is apparent, however, that the form gives a large power increase, enough for Goku, who was being easily beaten previously by Lord Slug, to now quickly overwhelm him.
"What? He's a Super Saiyan, yet not a Super Saiyan. So Pseudo Super Saiyan is what Super Saiyan was supposed to look like?"
by Kamikaze Failure December 12, 2017