Real Dictionary

jungle
singular noun: If you describe a place as a jungle, you are emphasizing that it is full of lots of things and very untidy.
singular noun: If you describe a situation as a jungle, you dislike it because it is complicated and difficult to get what you want from it.
variable noun: A jungle is a forest in a tropical country where large numbers of tall trees and plants grow very close together.

jungle in American English
land in a wet, tropical region, usually with large trees, dense underbrush, and a hot climate
noun: a wild land overgrown with dense vegetation, often nearly impenetrable, esp. tropical vegetation or a tropical rain forest

jungle in British English
noun: an equatorial forest area with luxuriant vegetation, often almost impenetrable