Best Friend For High School. A person that is your best friend now but you know that the second you leave high school you'll never speak to them again.
I'm really going to miss my BFFHS Sarah when we go away to college this summer.
The many ways (strange/unusual/paranormal/hallmark/cheesy/corny/sweet/loving/controlling) your BFF behaves towards you and your shared friendship of devotion, adherence, usage, characteristic ,state or condition; which designates a doctrine to your referenced designated BFF.
-ism suffix (Greek) - formation of nouns which denotes practice or action from verbs.
Janny: Car - you need to get off your whorish way's on FB!
Car: Janny, thanks for your bffism all these years! Without your bffism, I would not be the same.