The adjective ecstatic turns the noun "ecstasy" into a descriptive word. When Celine hit that high note, the audience was ecstatic.
Originally, ecstatic had religious connotations having to do with the sheer joy of knowing God or someone truly holy. That meaning remains today, but ecstatic now includes almost anything that's really pleasurable or wonderful. I was ecstatic at the news that I'd been nominated for an award. The entire world reacted with an ecstatic sense of glee when the Berlin Wall finally came down. The hangover the next day, though, wasn't so ecstatic.