Used prenominally for natural environments untouched by humans, such as forests, snow, or land.
See also: 処女林
その島には処女林が広がっている。
Virgin forest stretches across the island.
Specifically a male virgin; 処女 is usually female, though it can be used neutrally.
From Middle Chinese 處女 (tshjoX nrjoX). The kanji 処 means 'place' or 'to be in a state', and 女 means 'woman', together conveying 'a woman who stays at home', i.e., an unmarried maiden, later extended to 'virgin' and figurative 'untouched' uses.