Short for Crying On The Inside. Can be paired with lol as lolcoti or lol-coti to express "laughing out loud--crying on the inside". Also used by itself, usually as a sarcastic response to upsetting news.
"Great news! My company decided I was 'too valuable' in my current position to offer me that promotion <coti>!"
"Hey, I just heard my Ex is marrying a supermodel! lol-coti"