Lord’s universal form is the temporary imaginary resemblance of His personal form within the kingdom of Maya.
According to Śrīla Bhaktisiddhānta Sarasvatī Ṭhākura the word vairājaḥ in this verse indicates the totality of the individual conditioned souls who originally take birth from Brahmā and are amalgamated back into him at the time of annihilation. By the manifestation of the virāṭ-puruṣa, the universal form of the Lord, there is a temporary display of forms, qualities and activities within the material creation. But the entire cosmic scene reverts to inert formlessness when the creation is withdrawn by the Supreme Personality of Godhead. Therefore the Lord’s universal form cannot be accepted as an eternal form of the Lord. It is merely the temporary imaginary resemblance of His personal form within the kingdom of māyā. In the First Canto of the Śrīmad-Bhāgavatam, as well as in the Second Canto, the universal form of the Lord is clearly explained to be an imaginary form offered to the neophyte for meditation on God. Those who are excessively materialistic are totally unable to understand that the Supreme Personality of Godhead is actually sac-cid-ānanda-vigraha, or the eternal form of bliss and knowledge, transcendental to the exhibition of material energy. Therefore to encourage such gross materialists to become faithful theists, the Vedic literature instructs them to meditate upon the physical universe as the gigantic body of the Supreme Lord. This pantheistic conception does not reflect the ultimate reality of the Supreme Lord but is a technique to bring the mind gradually toward God.
Source: A.C. Bhaktivedanta Swami Prabhupada (2014 edition), “Srimad Bhagavatam”, Eleventh Canto, Chapter 03 – Text 12
