Venous a. : Of or pertaining to a vein or veins; as, the venous circulation of the blood.

Venous a. : Contained in the veins, or having the same qualities as if contained in the veins, that is, having a dark bluish color and containing an insufficient amount of oxygen so as no longer to be fit for oxygenating the tissues; -- said of the blood, and opposed to arterial.

Venous a. : Marked with veins; veined; as, a venous leaf.

Example:
Why is it important that Venous pressure becomes steadily lower as we get closer back to the right atrium?

Taxonomy
veins, blood, heart, arteries, body, deoxygenated blood, oxygenated blood, tissues, back to the heart, lungs, pulmonary veins, from the heart, hepatic portal vein, Venous insufficiency, Deep vein thrombosis, free encyclopedia, capillary beds, return blood.

Defination from the web:
venous valves that prevent blood from flowing back and pooling in the lower extremities due to the effects of gravity. ... A portal venous system is a series of veins or venules that directly connect two capillary beds. ...