n. In zoology and anatomy, the union, intercommunication, or inosculation of vessels of any system with one another, or with vessels of another system, as the arteries, veins, and lymphatics. In surgery, after ligation of an artery, collateral circulation is established by arterial anastomosis.n. The interlacing or network of any branched system, as the veins of leaves or the nervures of insects' wings. See cut under venation.n. In surgery, the establishment of communication between two canals or two portions of the same canal, usually the digestive tract, not previously in continuity.