(0. Fr. verdier, Med. Lat. viridarius), a term used in English forest law for a judicial officer appointed to look after what was known as the "vert" (0. Fr. verd, green; Lat. viridis), i.e. the forest trees and underwood in the royal forests. It was the verderer's duty to keep 'the assizes and attend to all matters relating to trespasses (see Forest Law).