The Collaborative International Dictionary of English v.0.48:

Potence \Po"tence\, n. [F., fr. LL. potentia staff, crutch, L.,
   might, power. See Potency.]
   Potency; capacity. [R.] --Sir W. Hamilton.
   [1913 Webster]

WordNet (r) 3.0 (2006):

potence
    n 1: the state of being potent; a male's capacity to have sexual
         intercourse [syn: potency, potence] [ant: impotence,
         impotency]