A portmanteau of "Karma" and "Armageddon." References "shit hitting the fan" in an extreme way while acknowledging one's contributions to that event.
Specifically, when all the (usually unpleasant) stuff you've done comes back to you at once.
The only way out is to take your licking, batten the hatches, pull back, and deal with the stuff one by one.
Man, my license was revoked for not paying those speeding tickets, my car got the boot from those unpaid parking tickets, bill collectors are calling, work's a mess from my calling in "sick," and my girlfriend found out about the affair when the other girl stopped by our place... Argh, it's karmageddon!