A point of horrid disgusting realization that you have made a terrible mistake. Unfortunately, it's too late for it to be undone.
A phrase which takes on meaning similar to "faux pas" or "sticking one's foot in one's mouth" but with more of a twist.
Imagine that you went out drinking heavily one night, came home, and went to sleep. The next day, you check your "Sent Email" folder and find that you sent ten emails between the hours of 3am and 5am: five of them sent to your ex-girlfriend, four sent to co-workers, and one sent to a local massage parlor inquiring if they "offer any additional services". When you were describing these happenings to a friend later, you would say, "Well, I really licked a bum's ass last night..." and then you would describe your actions in great detail.
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