limpen

verb1

1. •
   To make or become limp.

   • The fusion fires ebbing in the magnetic pinchtorus was a languid decay, a sorrowful limpening. Flaccid. 2010 "Ares Express" by Ian McDonald
   • At the bottom were the generous buttocks, a crinkly anus and a vaginal passage containing my rapidly limpening penis. 2010, "The Sex Sphere" by Rudy Rucker