In Mahābhārata (Mahabharata) and other Purāṇas (Purana) we find exceptionally skilled chariot-riding warriors (rathī; rathi) described as atiratha (the Sanskrit prefix ati- signifies ‘great’). But the word served as a terminology in ancient military science. In fact the greatest of the mahāratha (maharatha) or great chariot-riding warriors usually became famous as atiratha. In order to explain the characteristics of a mahāratha warrior, Śrīdharasvāmī (Sridharaswami), the commentator of Śrīmadbhāgavadgītā (Srimadbhagavadgita) cites a verse according to which a warrior skilled enough to wield every kind of weapon and capable of combatting ten thousand archers single-handedly is called a mahāratha –

eko dasasahasrāṇi yodhayed yastu dhanvinām
śastra śāstrapravīṇajña mahāratha iti smṛtaḥ.

In order to explain that an atiratha warrior is definitely greater than a mahāratha, Dikshitar quotes a verse. It says, when a warrior possessing all the above mentioned qualities becomes capable of vanquishing a multitude of opposing force, the epithet of an atiratha can be applied on him –

amitān yodhayetyaśca pūrvoktaguṇasaṃyutaḥ
vijñeyo atirathanāmnā śastrāstranipuṇastadā.

Śrīdharasvāmī also says while defining atiratha – amitān yodhayed yastu saṃprokto’tirathastu saḥ. 

In Udyogaparva of Mahābhārata, Bhīṣma (Bhisma) counts the number of atiratha warriors in the combatting parties of the Kauravas and the Pāṇḍavas (Pandavas). According to him the atiratha warriors on the Kaurava side were Droṇācārya (Dronacharya), Kṛtavarmā (Kritavarma), Śalya (Salya), Kṛpācārya (Kripacharya), Bāhlīkā (Bahlika) and he himself. The atiratha warriors on the other side, according to him, were Arjuna, his son Abhimanyu, Sātyaki (Satyaki), Dhṛṣṭadyumna (Dhrishtadyumna), Purajit and Ghaṭotkaca (Ghatotkacha).