The rare occurrence where something is so enjoyable that it causes your heart to go into a seizure-like state, inducing rapid, flailing limbs that detach themselves from over exertion after short periods of time. Exploding organs and the melting of both hemispheres of the brain are also signs of an ecstatafucktastic event. Despite such fatal events, most live through ecstatafucktastic moments.
"What if Mars collided with Earth... But it was actually a giant rock made out of Walrus bone marrow?" "That'd be so ecstatafucktastic... You don't even know."