cannot be known by any other pramāṇa, except the scripture
अनाद्यन्तंanādyantaṃ
which has no beginning and end
ब्रह्मbrahma
Brahman
पूर्णम्pūrṇam
infinite
महत्mahat
great
महःmahaḥ
light
Translation
Brahman (being infinity) is that in which nothing can be discarded and to which nothing can be added. It is beyond mind and organs and cannot be known by any pramāṇa (except the scripture). It has no beginning and end. It is infinite and the greatest light (as it illumines all – as it enables all cognitions).
Annotation
aprameyam – prameyam is a thing which can be known by a pramāṇa, valid means of knowledge. Brahman is aprameyam as it is not known by pramāṇa–s such as perception, inference, comparision etc., It can be realised only by a pure mind which has undergone the three–fold discipline of śravaṇa–manana–nididhyāsana (Jagadguru).