A sticker in messenger used to indicate, "I have stopped talking. You should also stop talking."
Although it also can imply that you like something, so it's still polite.
Friend: Are we still on for *that stupid event that you haphazardly agreed upon* tomorrow evening?
You: *Blue thumbs up*
Friend: Great! See you there!
the feeling of disappointment a guy feels when a girl claims to be a gamer to get attention from him, but then leaves him hanging when the time comes to actually play something. like blue balls, but with gaming instead of sex.
Jenny said she likes to play video games, but every time i suggest we kick on the xbox she runs off and leaves me with a major case of blue thumb.