There are a few interpretational stitches that occasionally plague Utena in translated venues ...
"Mokushiroku" is a Japanese word that basically refers to the Book of Revelations in the Christian Bible. As such, "apocalypse" means what it's supposed to mean: a revelation, as of fate. (In American culture, "apocalypse" has been diluted to also mean basically an end-of-world scenario, or scene of mass destruction.) "Zettai Unmei Mokushiroku", then, refers to a complete revelation of fate, an "absolute destiny apocalypse".
The song "Zettai Unmei Mokushiroku" sees several incarnations over the course of the series Shoujo Kakumei Utena. The first is the basically dark rock original version with a small chorus of five people, mostly women. This is the pre-duel chorus for the Seitokai arc, which follows the establishment of Utena as a Duellist, battling the machinations of the Ootori Gakuen Student Council. The second is an almost industrial version, where "banging on things" percussion is very prominent, and accompanies the "Black Rose" arc. The chorus is expanded here to include a very standing-out male baritone. The final incarnation of the TV series is the version sung by Ban'yuu Inryoku, J.A. Seazer's large chorus. The instrumentation in this mix is darker orchestral rock, kind of an odd cousin of Malice Mizer. (The pre-duel sequence here makes use of an elevator, and I wonder if this is at all connected with Mikage's elevator from the Black Rose arc, although it's obvious that it's not the same elevator. For the first two story arcs, Utena had to get to the duel arena by walking up a huge spiral staircase; I'm sure the elevator was a welcome addition ... )
The infamous ZUM also makes an appearance in the Utena live-action musical, and is basically a rehash of the industrial mix with an all-female choir (thankfully). The version accompanying the movie, Adolescence Mokushiroku (Revelations of Adolescence), is basically all orchestral, but doesn't have as heavy a feel to it as the Ban'yuu Inryoku version.
Some consider this one of the more pretentious Utena songs; this is possibly because they're forced to listen to it in the middle of an episode every time there's a duel (about 15 episodes in a 39 episode series).