ये त्वक्षरमनिर्देश्यमव्यक्तं पर्युपासते।सर्वत्रगमचिन्त्यं च कूटस्थमचलं ध्रुवम् ॥

Anirdesyam That which cannot be actually shown or which cannot be defined -- the Akshaa or Satchidananda Para Brahman is beyond the reach of the mind and speech. Why can It not be defined Because It is unmanifested. It does not have the four alities of manifested beings, vi.z, Jati (caste such as Brahmana, Kshatriya, etc.), Guna (attributes such as blueness, whiteness, tallness, shortness, etc.), Kriya (reading, walking, etc.), and Sambandha (like the relation between father and son).The unmanifest Incomprehensible by any of the organs of knowledge not manifest to any of the organs of knowledge.Upasana (worship) means sitting near. It is approaching the chosen ideal or object of worship by meditating on it, in accordance with the teachings of the scriptures and the spiritual preceptor, and dwelling steadily in the current of that one thought like a threat of oil poured from one vessel to another. It means continous and uninterrupted contemplation of God.The imperishable Brahman is omnipresent, pervading everything like the ether. It is unthinkable, because It is unmanifest. Whatever is visible to the senses can be thought of by the mind also. That which can be grasped by the organs of knowledge can be thought of by the mind also. But the Supreme Being is invisible to the senses and so cannot be grasped by the organs of knowledge and is, therefore, unthinkable