महाभारतः mahābhārataḥ - book-6, chapter-48, verse-21

सैन्धवप्रमुखैर्गुप्तः प्राच्यसौवीरकेकयैः ।
सहसा प्रत्युदीयाय भीष्मः शांतनवोऽर्जुनम् ॥२१॥

21. saindhavapramukhairguptaḥ prācyasauvīrakekayaiḥ ,
sahasā pratyudīyāya bhīṣmaḥ śāṁtanavo'rjunam.

21. saindhavapramukhaiḥ guptaḥ prācyasauvīrakekayaiḥ
sahasā pratyudīyāya bhīṣmaḥ śāntanavaḥ arjunam

21. śāntanavaḥ bhīṣmaḥ saindhavapramukhaiḥ
prācyasauvīrakekayaiḥ guptaḥ sahasā arjunam pratyudīyāya

21. Bhishma, the son of Shantanu, protected by the prominent Saindhavas, Pracyas, Sauviras, and Kekayas, suddenly confronted Arjuna.

Words meanings summery:

• सैन्धवप्रमुखैः (saindhavapramukhaiḥ) - by those led by the Saindhavas, by the principal Saindhavas

• गुप्तः (guptaḥ) - protected, guarded, hidden

• प्राच्यसौवीरकेकयैः (prācyasauvīrakekayaiḥ) - by the Pracyas, Sauviras, and Kekayas (names of tribes or regions)

• सहसा (sahasā) - suddenly, quickly, forcefully

• प्रत्युदीयाय (pratyudīyāya) - advanced towards, went against, confronted

• भीष्मः (bhīṣmaḥ) - Bhishma

• शान्तनवः (śāntanavaḥ) - Bhishma, the son of King Shantanu (son of Shantanu)

• अर्जुनम् (arjunam) - Arjuna

Words meanings and morphology

सैन्धवप्रमुखैः (saindhavapramukhaiḥ) - by those led by the Saindhavas, by the principal Saindhavas

(adjective)

Instrumental, masculine, plural of saindhavapramukha

saindhavapramukha - led by the Saindhavas; having Saindhava as chief; foremost of the Saindhavas

Compound type : bahuvrīhi (saindhava+pramukha)

• saindhava – of or belonging to the Sindhu region; a king of Sindhu; an inhabitant of Sindhu
  proper noun (masculine)
  derived from sindhu + aṇ (or related suffix)
• pramukha – chief, principal, foremost, led by
  adjective (masculine)
  Prefix: pra

Note: Qualifies the collective 'Pracyas, Sauviras, and Kekayas' as protecting Bhishma.

गुप्तः (guptaḥ) - protected, guarded, hidden

(adjective)

Nominative, masculine, singular of gupta

gupta - protected, guarded, hidden

Past Passive Participle

derived from root √gup (to protect, hide)

Root: √gup (class 1)

Note: Agrees with Bhishma.

प्राच्यसौवीरकेकयैः (prācyasauvīrakekayaiḥ) - by the Pracyas, Sauviras, and Kekayas (names of tribes or regions)

(proper noun)

Instrumental, masculine, plural of prācyasauvīrakekaya

prācyasauvīrakekaya - the Pracyas, Sauviras, and Kekayas (collective proper noun)

Compound type : dvandva (prācya+sauvīra+kekaya)

• prācya – eastern; a native of the eastern country
  proper noun (masculine)
  from prāc + ya
• sauvīra – name of a country or its inhabitants
  proper noun (masculine)
• kekaya – name of a country or its inhabitants; the Kekaya people
  proper noun (masculine)

Note: Indicates the means or agents of protection.

सहसा (sahasā) - suddenly, quickly, forcefully

(indeclinable)

प्रत्युदीयाय (pratyudīyāya) - advanced towards, went against, confronted

(verb)

3rd person , singular, active, perfect (liṭ) of √i

Perfect tense, 3rd person singular

From prati-ud-√i. 'īyāya' is a perfect tense form, cognate with forms of √yā.

Prefixes: prati+ud

Root: √i (class 2)

भीष्मः (bhīṣmaḥ) - Bhishma

(proper noun)

Nominative, masculine, singular of bhīṣma

bhīṣma - Bhishma (a renowned warrior and patriarch in the Mahabharata)

Note: Subject of the verb 'pratyudīyāya'.

शान्तनवः (śāntanavaḥ) - Bhishma, the son of King Shantanu (son of Shantanu)

(proper noun)

Nominative, masculine, singular of śāntanava

śāntanava - son of Shantanu

patronymic (taddhita suffix -a) from Shantanu

Note: In apposition to Bhishma.

अर्जुनम् (arjunam) - Arjuna

(proper noun)

Accusative, masculine, singular of arjuna

arjuna - Arjuna (a prominent Pandava prince and skilled archer)

Note: Object of the verb 'pratyudīyāya'.