Jungle Carbine was an informal term used for the Rifle No. 5 Mk I which was a derivative of the British Lee Enfield No. 4 Mk I

Lee-Enfield

The Lee-Enfield bolt-action, magazine-fed, repeating rifle was the main firearm used by the military forces of the British Empire and Commonwealth during the first half of the 20th century...

, designed not for jungle fighting but in response to a requirement for a "Shortened, Lightened" version of the No.4 rifle for airborne forces in the European theatre of operations. The end of the war in Europe overtook widespread issue of the No.5 and most of the operational use of this rifle occurred in post-war colonial campaigns such as the Malayan emergency, where engagement ranges tended to be shorter and its handier size and reduced weight were an advantage.