1.  A dense growth of brushwood, grasses, reeds, vines, etc.; an almost impenetrable thicket of trees, canes, and reedy vegetation, as in India, Africa, Australia, and Brazil.
"The jungles of India are of bamboos, canes, and other palms, very difficult to penetrate." [1913 Webster]

2.  A place of danger or ruthless competition for survival. [PJC]

3.  Anything which causes confusion or difficulty due to intricacy; as, a jungle of environmental regulations. [PJC]
"The latter, which resembles the domestic gamecock, is supposed to be one of the original species from which the domestic fowl was derived." [1913 Webster]

jungle, n.
1 a land overgrown with underwood or tangled vegetation, esp. in the tropics. b an area of such land.
2 a wild tangled mass.
3 a place of bewildering complexity or confusion, or of a struggle for survival (blackboard jungle).

Idiom:
jungle fever a severe form of malaria. law of the jungle a state of ruthless competition.

Derivative:
jungled adj. jungly adj.

Etymology:
Hindi jangal f. Skr. jangala desert, forest

N  complexity, complexness, complexus, complication, implication, intricacy, intrication, perplexity, network, labyrinth, wilderness, jungle, involution, raveling, entanglement, coil, sleave, tangled skein, knot, Gordian knot, wheels within wheels, kink, gnarl, knarl, webwork, difficulty, gnarled, knarled, complex, complexed, intricate, complicated, perplexed, involved, raveled, entangled, knotted, tangled, inextricable, irreducible.

N  vegetable, vegetable kingdom, flora, verdure, plant, tree, shrub, bush, creeper, herb, herbage, grass, annual, perennial, biennial, triennial, exotic, timber, forest, wood, woodlands, timberland, hurst, frith, holt, weald, park, chase, greenwood, brake, grove, copse, coppice, bocage, tope, clump of trees, thicket, spinet, spinney, underwood, brushwood, scrub, boscage, bosk, ceja, chaparal, motte, arboretum, bush, jungle, prairie, heath, heather, fern, bracken, furze, gorse, whin, grass, turf, pasture, pasturage, turbary, sedge, rush, weed, fungus, mushroom, toadstool, lichen, moss, conferva, mold, growth, alfalfa, alfilaria, banyan, blow, blowth, floret, petiole, pin grass, timothy, yam, yew, zinnia, foliage, branch, bough, ramage, stem, tigella, spray, leaf, flower, blossom, bine, flowering plant, timber tree, fruit tree, pulse, legume, vegetable, vegetal, vegetive, vegitous, herbaceous, herbal, botanic, sylvan, silvan, arborary, arboreous, arborescent, arborical, woody, grassy, verdant, verdurous, floral, mossy, lignous, ligneous, wooden, leguminous, vosky, cespitose, turf-like, turfy, endogenous, exogenous, green-robed senators of mighty woods, this is the forest primeval.

concrete jungle, jungle cat, jungle cock, jungle fever, jungle fowl, jungle gym, jungle hen, jungle rot, red jungle fowl