"It's a jungle out there" is an idiomatic English expression describing a dangerous and threatening situation. It often has the broader implication that the entire world is the proverbial "jungle," a dangerous environment filled with hazards in which all parties are out only for themselves. This expression draws on a long tradition in English idiom and literature of representing the natural world, and jungles in particular, as threatening and chaotic. The term is primarily American, although it also occurs in British English.
The expression is one of a number of English idioms in which the jungle stands for an uncivilized environment, a threatening natural world as opposed to the safety of the cultural world. "The law of the jungle" describes fundamental laws of human interaction, and is often used to describe brutal, unfair laws under which the strong exploit the weak, although ironically this is not consistent with the term's original use in Rudyard Kipling's "The Jungle Book." The term "jungle drums" refers to the informal methods of communication by which information often travels. "The concrete jungle" refers to cities, suggesting that cities are, in their own way, as dangerous and filled with predators as the wilderness.
All of these idioms, including "it's a jungle out there," draw on a conception of the difference between nature and civilization rooted deeply in Western thought. For example, Thomas Hobbes, a 17th-century philosopher, described the life of man in the state of nature as "solitary, poor, nasty, brutish and short." The behavior of animals served as an analogy for human behavior to writers like Shakespeare, who wrote that fish live in the sea "as men do a-land; the great ones eat up the little ones." Images of wild areas such as the jungle are therefore used to suggest dangerous environments in which predators thrive and the weak must look out for themselves.
"It's a jungle out there" has two slightly different common uses. The first is as a warning, and it usually includes the suggestion that the individual must look out for himself. In the second use, the expression is used to justify ruthless, competitive behavior on the part of the speaker. "I had to think of my own interests first," a speaker might argue, "it's a jungle out there." In this sense, the expression as the same meaning as the common saying "it's every man for himself."