na-adjective
contemplative; meditative
Describes a thoughtful, reflective state or attitude, often with a philosophical or introspective nuance.
彼は思索的な表情で窓の外を見ていた。
He was looking out the window with a contemplative expression.
この小説は思索的な内容が多い。
This novel has a lot of meditative content.
内省的 focuses on self-examination and introspection, whereas 思索的 can involve broader philosophical contemplation.
Compound of 思索 (shisaku, 'speculation; contemplation') + 的 (-teki, '-like; -ical'). The exact historical derivation is straightforward.