Mahabharata 12.187.1

युधिष्ठिर उवाच · yudhiṣṭhira uvāca

अध्यात्मं नाम यदिदं पुरुषस्येह चिन्त्यतेयदध्यात्मं यतश्चैतत्तन्मे ब्रूहि पितामह

adhyātmaṃ nāma yadidaṃ puruṣasyeha cintyateyadadhyātmaṃ yataścaitattanme brūhi pitāmaha

Our plain-language meaning of this verse is waiting for scholar review.