Bhagavad Gita
12.3

ये त्वक्षरमनिर्देश्यमव्यक्तं पर्युपासते । सर्वत्रगमचिन्त्यं च कूटस्थमचलं ध्रुवम् ॥

ye tvakṣaramanirdeśyamavyaktaṃ paryupāsate | sarvatragamacintyaṃ ca kūṭasthamacalaṃ dhruvam ||

Translation

But those who worship the Imperishable, the Indefinable, the Unmanifest — the Omnipresent, the Unthinkable, the Unchanging, the Unmovable, the Eternal —

Interpretation

A precise philosophical description of the formless Absolute: aksharama (imperishable), anirdesyam (indefinable — cannot be pointed to or described), avyaktam (unmanifest — beyond all phenomena), sarvatra-gam (omnipresent, going everywhere), achintyam (unthinkable — beyond mental concept), kutastham (unchanging, like the anvil that remains unmoved while all is hammered on it), achalam (immovable), dhruvam (eternal). Each term removes another limitation that the mind normally projects. The impersonal Absolute is identified by the negation of all finite characteristics.