The premature interruption of the proper sleeping off of a wicked hangover. On work days, typically due to an alarm clock or significant other, but can be any event that results in premature stupification due to early awakening from an alcohol induced stupor. Can also be used as a command by the person who's sounding them, or to describe one's painfully hungover state in the hours after initially hearing them.
Dude, you can't go to sleep now. It's gonna be Hells Bells in another hour.
Hells Bells sunshine! Get your drunken ass out of bed and go make me a living!
Man, I was feeling no pain when I got in last night, but it was Hells Bells when that fucking crew showed up next door at first light to tear out my neighbor's driveway.
Christ man, you look like shit!!! Hells Bells ringin' for you this morning? Yeah man, them bitches be clangin' for a MF!