noun
1. : one of the portal veins carrying blood from some of the posterior parts of the body to the kidneys in most lower vertebrates and including typically two trunks formed one for each kidney by the bifurcation of the caudal vein but enlarged or largely replaced by branches from the hind limbs in many of the higher forms
2. : either of a pair of veins in birds that originate like the renal portal veins of lower forms but pass through the corresponding kidney and enter the femoral vein without breaking into capillaries in the kidney