महाभारतः mahābhārataḥ - book-13, chapter-50, verse-3

पुरा महर्षिश्च्यवनो भार्गवो भरतर्षभ ।
उदवासकृतारम्भो बभूव सुमहाव्रतः ॥३॥

3. purā maharṣiścyavano bhārgavo bharatarṣabha ,
udavāsakṛtārambho babhūva sumahāvrataḥ.

3. purā maharṣiḥ cyavanaḥ bhārgavaḥ bharatarṣabha
udavāsakṛtārambhaḥ babhūva sumahāvrataḥ

3. bharatarṣabha purā maharṣiḥ cyavanaḥ bhārgavaḥ
udavāsakṛtārambhaḥ sumahāvrataḥ babhūva

3. O best among the Bharatas, in ancient times, the great sage Chyavana, a descendant of Bhṛgu, undertook the commencement of a water dwelling, and became a practitioner of very great spiritual disciplines (vrata).

Words meanings summery:

• पुरा (purā) - in ancient times (formerly, anciently, in old times)

• महर्षिः (maharṣiḥ) - the great sage (great sage, great seer)

• च्यवनः (cyavanaḥ) - the sage Chyavana (Chyavana (name of a sage))

• भार्गवः (bhārgavaḥ) - (Chyavana) the descendant of Bhṛgu (descendant of Bhṛgu, son of Bhṛgu)

• भरतर्षभ (bharatarṣabha) - O best among the Bharatas (a common epithet addressing the listener) (O best among Bharatas, O bull among Bharatas)

• उदवासकृतारम्भः (udavāsakṛtārambhaḥ) - one who had commenced the act of dwelling in water (one who has begun a water-dwelling)

• बभूव (babhūva) - became (became, was, happened)

• सुमहाव्रतः (sumahāvrataḥ) - one who practices extremely severe austerities (vrata) (one of very great vows/austerities/spiritual disciplines)

Words meanings and morphology

पुरा (purā) - in ancient times (formerly, anciently, in old times)

(indeclinable)

महर्षिः (maharṣiḥ) - the great sage (great sage, great seer)

(noun)

Nominative, masculine, singular of maharṣi

maharṣi - great sage, great seer; a class of divine beings

Compound of mahat and ṛṣi.

Compound type : karmadhāraya (mahat+ṛṣi)

• mahat – great, large, mighty
  adjective (neuter)
• ṛṣi – seer, sage, inspired poet
  noun (masculine)
  Root: ṛṣ (class 1)

च्यवनः (cyavanaḥ) - the sage Chyavana (Chyavana (name of a sage))

(proper noun)

Nominative, masculine, singular of cyavana

cyavana - Chyavana (name of a sage, son of Bhṛgu)

भार्गवः (bhārgavaḥ) - (Chyavana) the descendant of Bhṛgu (descendant of Bhṛgu, son of Bhṛgu)

(noun)

Nominative, masculine, singular of bhārgava

bhārgava - descendant of Bhṛgu, son of Bhṛgu; a name of Śukra (Venus)

Formed from Bhṛgu with a patronymic suffix -a.

भरतर्षभ (bharatarṣabha) - O best among the Bharatas (a common epithet addressing the listener) (O best among Bharatas, O bull among Bharatas)

(noun)

Vocative, masculine, singular of bharatarṣabha

bharatarṣabha - best among Bharatas, bull among Bharatas

Compound of Bharata and ṛṣabha.

Compound type : tatpuruṣa (bharata+ṛṣabha)

• bharata – a descendant of Bharata (name of an ancient king); a member of the Bharata lineage
  noun (masculine)
• ṛṣabha – bull; best, chief, excellent
  noun (masculine)

उदवासकृतारम्भः (udavāsakṛtārambhaḥ) - one who had commenced the act of dwelling in water (one who has begun a water-dwelling)

(noun)

Nominative, masculine, singular of udavāsakṛtārambha

udavāsakṛtārambha - one who has begun a water-dwelling

Compound of uda-vāsa, kṛta, and ārambha.

Compound type : bahuvrīhi (uda+vāsa+kṛta+ārambha)

• uda – water
  noun (neuter)
• vāsa – dwelling, residence
  noun (masculine)
  From root vas 'to dwell'.
  Root: vas (class 1)
• kṛta – done, made, performed
  adjective (neuter)
  Past Passive Participle
  From root kṛ 'to do'.
  Root: kṛ (class 8)
• ārambha – beginning, commencement, undertaking
  noun (masculine)
  From root rabh with prefix ā-.
  Prefix: ā
  Root: rabh (class 1)

बभूव (babhūva) - became (became, was, happened)

(verb)

3rd person , singular, active, perfect (liṭ) of bhū

Perfect tense, 3rd person singular

Root: bhū (class 1)

सुमहाव्रतः (sumahāvrataḥ) - one who practices extremely severe austerities (vrata) (one of very great vows/austerities/spiritual disciplines)

(adjective)

Nominative, masculine, singular of sumahāvrata

sumahāvrata - one who has very great vows, one who undertakes severe spiritual disciplines

Compound of su, mahā, and vrata.

Compound type : bahuvrīhi (su+mahā+vrata)

• su – good, well, excellent; intensely
  indeclinable
• mahā – great, large
  adjective
  Derived from mahat.
• vrata – vow, sacred observance, religious duty, spiritual discipline, austerity
  noun (neuter)