A fork of Rural Dictionary
The feeling the day after a night out, involving being severely hungover from excessive drinking or coming down from rec drugs (mostly cocaine and pills). Victim has 'the blues' and feels frail, old and ancient - like a caveman.
*throws up* "Ugh, i'm gonna have the caveman blues tomorrow.." *wakes up* "You alright mate? you look like shit!" "Nahhh, I've got some serious caveman blues.."