A competitive list of those of your friends who have vomited after drinking much alcohol. Usually, a "boot" consists of any and all alcohol related vomit in that one drinking session. Taking the lead on the boot list is a shameful act reserved for pussies and chicks who hang out too much with guys.
Dude, that's three, you've tied for the top of the boot list!
The fin created on one side of your hair/head when you vomit (boot) from drinking too much and then sleep in a pool of it. The fin formation is the result of it drying and creating the ultimate hair spiker.
Man, look at Tim—he's going to have a boot fin in the morning.