noun
stronghold; impregnable position
Refers to a firmly defended military position or, by extension, an unassailable stance in debate or competition. Somewhat formal and often used in strategic contexts.
敵軍は堅陣を築いて待ち構えていた。
The enemy forces had built a stronghold and were lying in wait.
彼の議論は堅陣で、反論の余地がなかった。
His argument was an impregnable position, leaving no room for rebuttal.
Compound of 堅 (firm, solid) and 陣 (camp, battle formation). The exact historical derivation is uncertain, but the word has been used in military and strategic contexts to denote a well-defended position.