Collateral circulation is the alternate circulation around a blocked artery or vein via another path, such as nearby minor vessels. Wikipedia

The alternate circulation around a blocked artery or vein via another path, such as nearby minor vessels Wikipedia Disambiguation

The circulation of blood through a network of vessels that is developed through enlargement of secondary vessels and use of existing anastomoses between adjacent vessels when a major vein or artery is functionally impaired, as by obstruction. Wiktionary

Circulation of blood through enlarged secondary vessels. Wiktionary (translation)