na-adjective, noun
pious; devout
Describes a deeply religious, reverent attitude or person. Often used in Christian contexts but applicable to any faith.
彼女は敬虔なクリスチャンです。
She is a devout Christian.
敬虔な祈りを捧げた。
They offered a pious prayer.
Search-only form; not a standard written variant.
信心深い also means 'pious' or 'devout', but emphasizes deep, personal faith and is more commonly used in everyday speech. 敬虔 is slightly more formal and often used in written or religious contexts.
From the kanji 敬 (respect, reverence) and 虔 (pious, respectful). The exact historical derivation is uncertain, but the compound has been used in Japanese to express religious devotion.