Two people are going at it in an outhouse, the man standing, and the woman bent over. Either while or after the man climaxes, he shoves the woman's head into the septic pit.
Similar to a swirly, only instead of a semi-clean flushing toilet, they just get lots of feces all over their head.

A portmanteau of carpe diem, a Latin phrase that means “Seize the Day!” and DM, which stands for Direct Messages. This word means seizing the day via DMs.