The small pointy fold of skin created when one wraps their hand into a fist but sticks their thumb straight out. The flubert apex will be found on the side opposite the thumb. Fluberts are occasionally touched by two friends who haven't seen each other in a while. One will yell "Flubert!" and then they will engage in the mashing together of their pointy skin mountains.

Literally everyone, ever. Including the writer of this definition.