महाभारतः mahābhārataḥ - book-7, chapter-19, verse-8

ग्रीवायां शूरसेनाश्च दरदा मद्रकेकयाः ।
गजाश्वरथपत्त्यौघास्तस्थुः शतसहस्रशः ॥८॥

8. grīvāyāṁ śūrasenāśca daradā madrakekayāḥ ,
gajāśvarathapattyaughāstasthuḥ śatasahasraśaḥ.

8. grīvāyāṃ śūrasenāḥ ca daradāḥ madrakekayāḥ
gajāśvarathapattyaughāḥ tasthuḥ śatasahasraśaḥ

8. grīvāyāṃ śūrasenāḥ ca daradāḥ madrakekayāḥ
gajāśvarathapattyaughāḥ śatasahasraśaḥ tasthuḥ

8. The Śūrasenas, Daradas, and Madra-Kekayas, along with their throngs of elephants, horses, chariots, and infantry, stood by the neck (of the battle formation) in hundreds of thousands.

Words meanings summery:

• ग्रीवायां (grīvāyāṁ) - at the neck (of the battle formation) (in the neck, at the neck)

• शूरसेनाः (śūrasenāḥ) - the Śūrasenas (a people/tribe)

• च (ca) - and

• दरदाः (daradāḥ) - the Daradas (a people/tribe)

• मद्रकेकयाः (madrakekayāḥ) - the Madras and Kekayas

• गजाश्वरथपत्त्यौघाः (gajāśvarathapattyaughāḥ) - throngs of elephants, horses, chariots, and infantry

• तस्थुः (tasthuḥ) - they stood, they remained

• शतसहस्रशः (śatasahasraśaḥ) - by hundreds of thousands, in hundreds of thousands

Words meanings and morphology

ग्रीवायां (grīvāyāṁ) - at the neck (of the battle formation) (in the neck, at the neck)

(noun)

Locative, feminine, singular of grīvā

grīvā - neck; forepart

शूरसेनाः (śūrasenāḥ) - the Śūrasenas (a people/tribe)

(proper noun)

Nominative, masculine, plural of śūrasena

śūrasena - a name of an ancient Indian tribe or kingdom

च (ca) - and

(indeclinable)

दरदाः (daradāḥ) - the Daradas (a people/tribe)

(proper noun)

Nominative, masculine, plural of darada

darada - a name of an ancient Indian tribe, usually located in the northwest

मद्रकेकयाः (madrakekayāḥ) - the Madras and Kekayas

(proper noun)

Nominative, masculine, plural of madrakekaya

madrakekaya - the Madras and Kekayas (a dual compound) or a collective name for both groups

Compound type : itaretara-dvandva (madra+kekaya)

• madra – a name of a people/kingdom, usually in Punjab
  proper noun (masculine)
• kekaya – a name of a people/kingdom, usually in Punjab
  proper noun (masculine)

गजाश्वरथपत्त्यौघाः (gajāśvarathapattyaughāḥ) - throngs of elephants, horses, chariots, and infantry

(noun)

Nominative, masculine, plural of gajāśvarathapattyaugha

gajāśvarathapattyaugha - throngs of elephants, horses, chariots, and foot soldiers

Compound type : itaretara-dvandva followed by tatpurusha (gaja+aśva+ratha+patti+ogha)

• gaja – elephant
  noun (masculine)
• aśva – horse
  noun (masculine)
• ratha – chariot
  noun (masculine)
• patti – foot soldier, infantry
  noun (masculine)
• ogha – flood, current, multitude, throng
  noun (masculine)

Note: The entire compound acts as the subject referring to the collective forces.

तस्थुः (tasthuḥ) - they stood, they remained

(verb)

3rd person , plural, active, perfect (lit) of sthā

perfect active 3rd plural

Reduplicated perfect form of √sthā.

Root: sthā (class 1)

शतसहस्रशः (śatasahasraśaḥ) - by hundreds of thousands, in hundreds of thousands

(indeclinable)

Formed with the suffix -śaḥ indicating 'by groups of' or 'in numbers of'.

Note: Adverbial use.