When your dick's size becomes so large that it reaches a critical mass and begins to collapse in on the balls. The dick then retracts inside of the pelvis and forms a psuedo vagina.
"Hey Bobby what's that glowing rod coming from your pants?!" "Oh thats just a dick implosion, an interstellar mass larger than the sun retreating back into itself so as to hide its awesomeness from the world because the world cannot understand it yet."
by H.R. Blunderbuss March 21, 2013