A large drum historically used on battlefields to signal troops or boost morale; now seen mainly in historical reenactments, festivals, or traditional performances.
In battles of the Warring States period, the sound of war drums boosted the soldiers' morale.
Compound of 陣 (jin, 'battle formation, camp') and 太鼓 (taiko, 'drum'). The reading じんだいこ reflects rendaku voicing on the second element.