Flextrubate 

The act of flexing with one arm in a mirror whilst mastrubating in a mirror to yourself. Usually performed by men named Kenny or Thad.

After the party was a flop, Kenny went home to lick his wounds and flextrubate.

Flextrubate by Cooter75 August 6, 2019

Flexurbate 

The act of flexing your muscles infront of a mirror while using the other arm to vigorously masturbate to your own reflection.

After a long day at the gym, I took it upon myself to flexurbate to admire my rock hard pecs.

Flexurbate by atheos01 April 26, 2015