Urinating backwards. Also an animal such as a raccoon that urinates backwards. From the Latin retro- (back) + mingent from mingere (to urinate).
"You have revealed yourself as a miserable, carping, retromingent vigilante, and I for one am sick of wasting my time communicating with you" (Benjamin C. Bradlee, Editor, The Washington Post).
Outdated zoological term which refers to animals which piss backwards. Like a cow. This word is also an excellent insult for fat women who like to piss while kneeling down.
'I hate bumming retromingents while they're pissing'
'She looks positively retromingent'