two-fist smashin' it
v. 
the action of auto-stimulation by use of two hands clinched in a fist shape.

*first discovered in the CNN building where a wonderful Pithecia pithecia was viewed in it's cage engaging in 'two-fist smashin' it'
Yo, homie D-Loc been in lock down for so long man.  i bet he be two-fist smashin' it every night