pri·a·pism 
(prīə-pĭz′əm)
(prīə-pĭz′əm)n.
Persistent, usually painful erection of the penis, especially as a consequence of disease and not related to sexual arousal.
[French priapisme, from Late Latin priāpismus, from Greek priāpismos, from priāpizein, to have an erection, from Priāpos, Priapus.]