The way to describe the behavior of a bi-polar lover. Traditionally used when a great date with said individual is followed by an extremely bad or awkward date.
Joel: hey how was your date last night, you were really excited?
Brian: horrible we had a great time last week but last night she spent the whole date texting.
Joel: she is a total hot fish cold fish... get out now.
It's like when you go into the northern woods for a few hours to hunt. When you get back up to go home you have to look behind you and make sure your ass wasn't left behind. That is ass cold