Ghast is an element that has an ID of 20. It is found in Monsters Group. It's icon is a ghast head.
Ghast was originally intended to be Ghost, but since it doesn't exists in Minecraft and it can't be used to create anything, it was renamed to Ghast. The recipe however, was still Ghost's recipe.
Possible recipes would be:
Used to Create Edit
This might be added in future development.
“Ghasts are huge, floating Nether mobs that shoot explosive fireballs at the player.” ― Minecraft Gamepedia