1. A way of sarcastically saying goodbye.
2. A response for when someone says something unbelievable. (More accent is used on "cool")
3. A way of saying you're going to ignore someone.
The louder you say it the better.
Person A:"Hey I'll see you tomorrow."
Person B:"Whatever, cool-later."
Person A:"Jason had sex with five chicks last night!"
"Pssh, I gave that biatch the old Cool Later."