1. To hold an alcoholic drink for an inordinate amount of time.
2. To pretend to be drinking hoping no one sees that your alcoholic drink has been at the same level for a minimum of at least 40 minutes.
3. Challenging others to drinking contests in hope that they are too drunk to see you haven't been drinking at all.
Also see "Nursing"
Milo: "Screw you bro! Don't challenge a Beerlympic champion when you've been kostasing your beer all night!"