From the Kingdom Hearts Wiki: A world of information not accessible by Gummiship
Yoggy Slice (ヤギスライス, Yagi Suraisu?, lit. "Goat Slice") is a technique that appears in Kingdom Hearts 3D: Dream Drop Distance. It allows the user to attack with its horns. It is part of the Yoggy Flurry command.
Learning Yoggy Slice
Kingdom Hearts 3D: Dream Drop Distance