The instant feeling of regret upon realizing that the text message you just sent was either unfunny, rude, or off topic to the point that you wished you had never sent it in the first place.
After sending a text I realized that the recipient may not think that it was as funny as I thought it was. I totally regrext that one!
Feeling you get the morning after throwing up/ falling over/ talking to the wall about the universe being made out of segments on account on having over-indulged in the drugketamine.
I thought I threw up on my front doorstep last night, but when I came round I realised it was my flatmate's bed. Major regretamine.
A phrase that has been ironically quoted by many vtubers after a Twitter userposted screenshots of an alleged vtuber asking for free art saying "I'm a vtuber and you'll regret this" after the artist refused.