योगवासिष्ठः yogavāsiṣṭhaḥ - book-7, chapter-92, verse-18

मर्मकर्मकरैकात्मा हृद्गुहागेहकेसरी ।
नित्यमेकान्तपथिकः सारविज्जातवेदसः ॥ १८ ॥

marmakarmakaraikātmā hṛdguhāgehakesarī ,
nityamekāntapathikaḥ sāravijjātavedasaḥ 18

18. marmakarmakaraikātmā hṛdguhāgehakesarī
nityam ekāntapathikaḥ sāravit jātavedasaḥ

18. marmakarmakaraikātmā hṛdguhāgehakesarī
nityam ekāntapathikaḥ sāravit jātavedasaḥ

18. He is the one (ātman) who performs the actions that affect the vital points, the lion residing in the cave-like abode of the heart. He is always a solitary traveler, and the knower of the essence (sāra) of all that is manifest (jātavedas).

Words meanings summery:

• मर्मकर्मकरैकात्मा (marmakarmakaraikātmā) - the sole self (ātman) that performs vital actions

• हृद्गुहागेहकेसरी (hṛdguhāgehakesarī) - the lion in the cave-like abode of the heart

• नित्यम् (nityam) - always, perpetually, constantly

• एकान्तपथिकः (ekāntapathikaḥ) - a solitary traveler, one who travels alone

• सारवित् (sāravit) - knower of the essence

• जातवेदसः (jātavedasaḥ) - of Jātavedas (fire, or all born/manifested things)

Words meanings and morphology

मर्मकर्मकरैकात्मा (marmakarmakaraikātmā) - the sole self (ātman) that performs vital actions

(noun)

Nominative, masculine, singular of marmakarmakaraikātman

marmakarmakaraikātman - the single self performing actions on vital spots

Compound type : bahuvrīhi/karmadhāraya (marman+karman+kara+eka+ātman)

• marman – vital spot, vulnerable point, secret
  noun (neuter)
• karman – action, deed, work, ritual (karma)
  noun (neuter)
  Root: kṛ (class 8)
• kara – doer, maker, performing
  noun (masculine)
  Agent Noun (ac)
  Derived from root kṛ (to do, make) with ac suffix.
  Root: kṛ (class 8)
• eka – one, sole, unique, single
  adjective
• ātman – self, soul, spirit, essence
  noun (masculine)

हृद्गुहागेहकेसरी (hṛdguhāgehakesarī) - the lion in the cave-like abode of the heart

(noun)

Nominative, masculine, singular of hṛdguhāgehakesarin

hṛdguhāgehakesarin - lion whose abode is the heart-cave

Compound type : tatpuruṣa (hṛd+guhā+geha+kesarin)

• hṛd – heart, mind, soul
  noun (neuter)
• guhā – cave, cavern, recess
  noun (feminine)
• geha – house, abode, dwelling
  noun (neuter)
• kesarin – lion (having a mane)
  noun (masculine)

नित्यम् (nityam) - always, perpetually, constantly

(indeclinable)

Note: Used adverbially (accusative singular neuter of adjective nitya)

एकान्तपथिकः (ekāntapathikaḥ) - a solitary traveler, one who travels alone

(noun)

Nominative, masculine, singular of ekāntapathika

ekāntapathika - solitary traveler

Compound type : karmadhāraya (ekānta+pathika)

• ekānta – solitary, exclusive, private, secluded
  adjective
• pathika – traveler, wanderer, wayfarer
  noun (masculine)

सारवित् (sāravit) - knower of the essence

(noun)

Nominative, masculine, singular of sāravid

sāravid - knower of the essence

Agent Noun

Derived from root vid (to know) preceded by sāra.

Compound type : tatpuruṣa (sāra+vid)

• sāra – essence, core, pith, best part
  noun (masculine)
• vid – knower, understanding
  noun (masculine)
  Agent Noun
  Derived from root vid (to know).
  Root: vid (class 2)

जातवेदसः (jātavedasaḥ) - of Jātavedas (fire, or all born/manifested things)

(noun)

Genitive, masculine, singular of jātavedas

jātavedas - fire, Agni; one who possesses knowledge of all that is born/created; all generated knowledge