definition of 5th generation war is as follows:

a war in which we engage ENEMY by using the social media and diverting their youth’s mind against their country and leaders.

Now I will go with all of it for those looking for complete elaboration and for those looking for the scholarly article about the 5th generation war.

The future of the ADF is ‘fifth generation’, or at least the Chiefs of Army, Navy and Air Force think so. It might’ve been just a passing fad, given that the term originated as a company marketing slogan selling a long-delayed fast jet. But in recent years the expression has morphed into a useful buzzword encapsulating several deeper concepts. At its core, ‘ the fifth generation’ is all about ideas, about how we conceive of waging tomorrow’s wars—and preparing for them. It encompasses four major approaches:

Networks. Modern war uses extensive digital networks. Conceptually, four interconnected and interdependent virtual grids—information, sensing, effects, and command—overlie the operational theatre. The various force elements are interacting nodes on the grids that can each receive, act on and pass forward data.
Combat cloud. Working together, the grids can form a virtual combat cloud—akin to commercial cloud computing—that allows users to pull and add data as necessary. The result is longer-range tactical engagements. It’s no more, ‘Fire when you see the whites of their eyes’, but rather, ‘Engage when a symbol labeled “adversary” appears on a shared display’.
Multi-domain battle. There are five operational domains: land, sea, air, space and cyber. The key animating idea is cross-domain synergy, where force is applied across two or more domains in a complementary manner (PDF) to achieve an operational advantage.
Fusion warfare. The fusion warfare concept addresses command and control concerns arising from additional information flows, software incompatibilities and intrinsic vulnerabilities to attack and deception.
The order of these approaches mostly reflects the sequence in which they’ve been incorporated into the concept of fifth-generation warfare.