A jungle is a wilderness of dense overgrowth found on planets. Often in places with a tropical climate.
Soukara had a large jungle near its Dominion base. In 2374, Worf and Jadzia Dax arranged to meet Lasaran in the jungle. They began to make their way through, until Jadzia was injured in a Jem'Hadar attack. Worf later left Jadzia behind to continue, but changed his mind and returned to her. (DS9: "Change of Heart")