The Collaborative International Dictionary of English v.0.48:

Retromingent \Re`tro*min"gent\, a. [Pref. retro- + L. mingens,
   p. pr. of mingere to urinate.]
   Organized so as to discharge the urine backward. -- n.
   (Zool.) An animal that discharges its urine backward.
   [1913 Webster]