trench derby

== English == === Alternative forms === trench-derby === Noun === trench derby (plural trench derbies) (military slang, World War I) A tin hat. === References === Lighter, Jonathan (1972), “The Slang of the American Expeditionary Forces in Europe, 1917-1919: An Historical Glossary”, in American Speech‎[1], volume 47, number 1/2, page 113