|This article may or may not be a stub, but it's definitely missing something.|
Specifically: Formatting the input, and tactics.
You can help the Street Fighter Wiki by giving us what we need.
The Psycho Headbutt (サイコヘッドバット, Saiko Heddobatto) is one of Gill's special attacks.
Executed by performing a quarter-circle backward motion and pressing punch, the attack simply sees Gill hop and thrust his head down in a headbutting attack. The attack is mostly used as a part of a combo.  Urien possesses a functionally similar move, but uses charge motions and electrocutes instead.
- Interestingly enough, Psycho Headbutt shares the same naming scheme as most abilities of the Psycho Power energy, although this could possibly be nothing more than a coincidental occurrence.