Longman Dictionary of Contemporary English
Wiktionary
n. 1 (context uncountable English) Warfare in which opposing sides occupy trenches and repeatedly fire at one another; usually involving high casualty rates over a long period of time. 2 (context uncountable by extension euphemistic English) Fighting of any sort which offers no hope of ending soon.
Wikipedia
Trench warfare is a type of land warfare using occupied fighting lines consisting largely of trenches, in which troops are significantly protected from the enemy's small arms fire and are substantially sheltered from artillery. The most famous use of trench warfare is the Western Front in World War I. It has become a byword for stalemate, attrition, sieges and futility in conflict.
Trench warfare occurred when a revolution in firepower was not matched by similar advances in mobility, resulting in a grueling form of warfare in which the defender held the advantage. On the Western Front in 1914–18, both sides constructed elaborate trench and dugout systems opposing each other along a front, protected from assault by barbed wire, mines, and other obstacles. The area between opposing trench lines (known as " no man's land") was fully exposed to artillery fire from both sides. Attacks, even if successful, often sustained severe casualties.
With the development of armoured warfare, emphasis on trench warfare has declined, but still occurs where battle-lines become static.
Usage examples of "trench warfare".
Fighting from building to building inside the great stone walls of Diocletian's palace had been every bit as appalling as trench warfare in France a quarter of a century before.
From the beginning of October until almost the end of November 1944, however, it would be involved in static, trench warfare, more reminiscent of World War I than World War II.
The Allies, however, soon halted the German army at the Marne River, and the war in the West settled down to four years of trench warfare--the static or at a standstill kind of war described in the discussion of Chapter 6 in this guidebook.
Humans and their genetically engineered allies had been forced into World-War-I-style trench warfare by this.
He had been a member of a Storm battalion in the World War: one of the elite units pulled from the front lines to break the deadly cycle of trench warfare.
After it, with the advent of winter, came the slow deadly sinking into the stalemate of trench warfare.