Atidhūmra (Atidhumra) is one of the one thousand and eight epithets of Śiva Mahādeva (Siva Mahadeva). The famous commentator Nīlakaṇṭha (Nilakantha) explains this epithet as –

atidhūmraḥ kālāgnirūpeṇa sarvadāhakāle’tyantadhūmramayaḥ.

Śiva, the destroyer of the cosmos, manifests as kālāgni (kalagni) or the cataclysmic fire causing the end of the universe at the time of pralaya (equivalent of the doomsday in Hindu mythology). Because Śiva is imagined as the calamitous fire of pralaya, emitting smoke profusely and shrouded in that very smoke, the epithet of Atidhūmra has been associated with him. Etymologically, the word is an adjective which means ‘a great amount of smoke’.