Refers to a persons behavior during the period of time from when they decide to quit their job until they actually hand in their resignation. A person who has pre-quit is treated like a regular employee but they do not actually get a lot done ( or they get even less than usual done). Most of their time is spent preparing for their next gig. Their day is one entire work break.
"Hey, did you notice that Miller came in late today".
"Yes, he is pre-quit"