The ruling is the latest twist in a decade-long UK chocolate wars saga between Nestle and Cadbury.
The Dairy Milk maker failed in its own attempt to trademark the shade of purple it uses after Nestle complained.
But on Wednesday, it was the Cadbury bosses celebrating the latest attempt to foil KitKat's plans.
Nestle claimed that the shape of the bar was so unique, it should be protected by law.
But time after time, judges have thrown out the attempt.