na-adjective, noun
Describes unwavering chastity, typically of a wife toward her husband. Often used in formal or literary contexts.
彼女は貞操堅固な妻として知られている。
She is known as a wife of steadfast chastity.
昔の女性には貞操堅固が求められた。
Women in the past were expected to be strictly chaste.
A yojijukugo (four-character compound) combining 貞操 (chastity) and 堅固 (firm, steadfast). The exact historical derivation is uncertain, but it follows a common pattern of pairing a virtue with a reinforcing adjective.