Forest or woodland having a mature or overly mature ecosystem more or less uninfluenced by human activity WordNet 3.0 & Open English WordNet

An old-growth forest, sometimes synonymous with primary forest, virgin forest, late seral forest, primeval forest, first-growth forest, or mature forest—is a forest that has attained great age without significant disturbance, and thereby exhibits unique ecological features, and might be classified as a climax community. Wikipedia

Ancient woodland or old-growth forest Wikipedia Disambiguation

Type of forest characterized by stands of seral or climax species usually well past the age of maturity, large in diameter relative to species and site potential, and exhibiting decadence, low growth rates, dead and dying trees and snags Wikidata

A forest area that has developed free from the influence of humans and remains largely unaffected by their activities. OmegaWiki

Forest which originally covered a region before changes in the environment brought about by people. OmegaWiki

A forest that has attained great age without significant disturbance. Wiktionary

Forest that has attained great age without significant disturbance. Wiktionary (translation)

A forest being more or less free from human ecological disturbance. Wiktionary

Forest free from disturbance. Wiktionary (translation)