Atidīpta (Atidipta) is one of the one thousand and eight names of Śiva (Siva). Attempting to explain this epithet of Śiva, the famous annotator Nīlakaṇṭha (Nilakantha) observes –

atidīptaḥ koṭisūryapratīkāśaḥ śatrutejo’bhibhāvaḥ.

The vast form of the Supreme Being that comes to our imagination is essentially full of divine brightness and splendour incomparable to anything worldly. No earthly being’s normal eyes can tolerate the fierce splendour. Bhagavadgītā (Bhagavadgita) observes, while describing the magnanimous form Kṛṣṇa (Krishna) showed Arjuna to convince him that He is the very force running the cosmos, that the brightness of a thousand suns together in the sky might be a match for his splendour –

divi sūryasahasrasya bhaved yugapadutthitā
yadi bhaḥ sadṛśī sā syādbhāsastasya mahātmanaḥ. 

Śiva, another manifestation of the Supreme Being, is known as Atidīpta because of the divine splendour of His vast form.

Whenever the majestic divinity of the Supreme Being is described, it is a common trait among the descriptions to mention the adjective of dīptimān (diptiman) or an equivalent, referring to His grand splendour and brightness. Elsewhere in Bhagavadgītā we find a dsimilar description –

nabhaspṛśam dīptamanekavarṇaṃ vyāttānanaṃ dīptaviśalanetram.