From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
First, Gohan puts his hands above his head like the normal Masenko, but keeps charging it until it forms a sphere of energy. Next, he grabs the sphere of energy with his hand and draws it back up to his side. Finally, Gohan shouts, "Masenko!" and throws the attack at his opponent, inflicting a great amount of damage.
Dragon Ball Z
Gohan used this attack in his battle against Freeza in his Second form. After he witnessed his friend, Kuririn, being nearly killed by Second Form Freeza, an enraged Gohan attacked him with a powerful barrage of punches, kicks, and rapid energy blasts, knocking the tyrant down to the ground and creating a massive dome of energy where he layed. Gohan then charged and fired the Masendan down at the massive energy dome and created a huge explosion, greatly injuring Second Form Freeza.
It is named Masenkō Aratame (魔閃光 改, Masenkō Aratame; Literally meaning "Demon Flash Change") in Dragon Ball Heroes.