just as in the urban definition of "sorry for partying," this right here is an add-on to the "sorry for partying" phrase. as we all know, we should never apologize for being awesome, being a complete bro, and for "partying." Party fingers is a gesture you make when you use the phrase sorry for partying. Just made a behind the back beer pong shot on a solo cup for the win? here is where you say "sorry for partying" while bringing your hands palms facing down up to around mouth/nose level in a comfortable fashion (or in a BRO fashion, if i may), extend fingers, and then wiggle them up and down like the winner you are. This gesture can also be used as a silent "sorry for partying" gesture, when you feel that your bro-manship after committing an act of supreme partying is so vast and so awesome that actually saying the phrase "sorry for partying" is beneath you, this when the silent party fingers is quite useful.
Now, my fellow bros, utilize this to your advantage, and may it fill you and your days with complete bliss. And of course, i apologize for partying (but not really though).
you just sinked a behind the back shot in beer pong on the solo cup for the win
option 1."sorry about it" (party fingers)
option 2. "sorry i'm not sorry" (party fingers)
option 3. "sorry for partying (party fingers)