True mastery of the cock requires regular practice.
Cockmastery can NOT be achieved by masturbating as this only results in the mastery of ONE cock (ones own), not cocks in general.
Therefore a cockmaster is a male who is thought to handle other peoples penises frequently, thereby aquiring skills that have to be considered masterful.
"Piss off, cockmaster."
The Yoda of the cock world.
It is an insult used to question the sexuality of the targeted person, who is usually male, or to express general disdain for them.