महाभारतः mahābhārataḥ - book-13, chapter-3, verse-3

तेन ह्यमितवीर्येण वसिष्ठस्य महात्मनः ।
हतं पुत्रशतं सद्यस्तपसा प्रपितामह ॥३॥

3. tena hyamitavīryeṇa vasiṣṭhasya mahātmanaḥ ,
hataṁ putraśataṁ sadyastapasā prapitāmaha.

3. tena hi amitavīryeṇa vasiṣṭhasya mahātmanaḥ
hatam putraśatam sadyaḥ tapasā prapitāmaha

3. hi prapitāmaha tena amitavīryeṇa vasiṣṭhasya
mahātmanaḥ putraśatam tapasā sadyaḥ hatam

3. Indeed, O great-grandfather, by that one of immeasurable valor (Viśvāmitra), a hundred sons of the great-souled Vasiṣṭha were immediately killed through the power of his spiritual austerity (tapas).

Words meanings summery:

• तेन (tena) - by Viśvāmitra (by that (one), by him)

• हि (hi) - indeed, emphasizing the statement (indeed, surely, for)

• अमितवीर्येण (amitavīryeṇa) - by Viśvāmitra, who possessed immeasurable valor (by one of immeasurable valor, by the immensely powerful one)

• वसिष्ठस्य (vasiṣṭhasya) - of the sage Vasiṣṭha (of Vasiṣṭha)

• महात्मनः (mahātmanaḥ) - of the great-souled Vasiṣṭha (of the great-souled, of the magnanimous)

• हतम् (hatam) - killed, referring to the sons (killed, destroyed)

• पुत्रशतम् (putraśatam) - the hundred sons of Vasiṣṭha (a hundred sons)

• सद्यः (sadyaḥ) - immediately, without delay (immediately, at once, instantly)

• तपसा (tapasā) - by the spiritual power gained through ascetic practices (tapas) (by austerity, by spiritual fervor, by ascetic power)

• प्रपितामह (prapitāmaha) - O great-grandfather Bhīṣma (O great-grandfather)

Words meanings and morphology

तेन (tena) - by Viśvāmitra (by that (one), by him)

(pronoun)

Instrumental, masculine, singular of tad

tad - that, it, he, she

हि (hi) - indeed, emphasizing the statement (indeed, surely, for)

(indeclinable)

अमितवीर्येण (amitavīryeṇa) - by Viśvāmitra, who possessed immeasurable valor (by one of immeasurable valor, by the immensely powerful one)

(adjective)

Instrumental, masculine, singular of amitavīrya

amitavīrya - of immeasurable strength or valor

Compound type : bahuvrihi (amita+vīrya)

• amita – unmeasured, immense, infinite
  adjective
  past passive participle
  P.P.P. from root mā (to measure) with prefix a- (negation)
  Prefix: a
  Root: mā (class 2)
• vīrya – valor, strength, potency, heroism
  noun (neuter)
  Root: vīr

वसिष्ठस्य (vasiṣṭhasya) - of the sage Vasiṣṭha (of Vasiṣṭha)

(proper noun)

Genitive, masculine, singular of vasiṣṭha

vasiṣṭha - a proper name, name of a celebrated Vedic sage

महात्मनः (mahātmanaḥ) - of the great-souled Vasiṣṭha (of the great-souled, of the magnanimous)

(adjective)

Genitive, masculine, singular of mahātman

mahātman - great-souled, magnanimous, noble

Compound type : bahuvrihi (mahat+ātman)

• mahat – great, large, immense
  adjective
• ātman – self, soul, spirit, essential nature
  noun (masculine)

हतम् (hatam) - killed, referring to the sons (killed, destroyed)

(adjective)

Nominative, neuter, singular of han

han - to strike, to kill, to destroy

past passive participle

Past Passive Participle of root han

Root: han (class 2)

Note: modifies putraśatam

पुत्रशतम् (putraśatam) - the hundred sons of Vasiṣṭha (a hundred sons)

(noun)

Accusative, neuter, singular of putraśata

putraśata - a hundred sons

Compound type : tatpurusha (putra+śata)

• putra – son, child
  noun (masculine)
• śata – hundred
  noun (neuter)

Note: refers to "a hundred (of) sons", treated as a singular collective noun

सद्यः (sadyaḥ) - immediately, without delay (immediately, at once, instantly)

(indeclinable)

तपसा (tapasā) - by the spiritual power gained through ascetic practices (tapas) (by austerity, by spiritual fervor, by ascetic power)

(noun)

Instrumental, neuter, singular of tapas

tapas - austerity, heat, spiritual fervor, asceticism, penance

Root: tap (class 1)

प्रपितामह (prapitāmaha) - O great-grandfather Bhīṣma (O great-grandfather)

(noun)

Vocative, masculine, singular of prapitāmaha

prapitāmaha - great-grandfather

Compound type : tatpurusha (pra+pitāmaha)

• pra – before, forward, forth
  indeclinable
  prefix indicating "great-" or "fore-"
• pitāmaha – grandfather
  noun (masculine)