योगवासिष्ठः yogavāsiṣṭhaḥ - book-6, chapter-15, verse-16

उद्गीर्णमन्त्रनिचयान्स्वाहाकारनिभस्वनान् ।
अस्थिनैकतडित्पुञ्जनीलमेघसमोपमान् ॥ १६ ॥

udgīrṇamantranicayānsvāhākāranibhasvanān ,
asthinaikataḍitpuñjanīlameghasamopamān 16

16. udgīrṇamantranicayān svāhākāranibhasvanān
asthinaikatadiṭpuñjanīlameghasamopamān

16. udgīrṇamantranicayān svāhākāranibhasvanān
asthinaikatadiṭpuñjanīlameghasamopamān

16. From whom collections of mantras were uttered, whose cries resembled the sacred "Svāhā" sound, and who resembled numerous heaps of bone-white lightning against dark blue clouds.

Words meanings summery:

• उद्गीर्णमन्त्रनिचयान् (udgīrṇamantranicayān) - from whom collections of mantras have been uttered

• स्वाहाकारनिभस्वनान् (svāhākāranibhasvanān) - having sounds resembling the syllable "Svāhā"

• अस्थिनैकतदिट्पुञ्जनीलमेघसमोपमान् (asthinaikatadiṭpuñjanīlameghasamopamān) - resembling many bone-white heaps of lightning and dark blue clouds

Words meanings and morphology

उद्गीर्णमन्त्रनिचयान् (udgīrṇamantranicayān) - from whom collections of mantras have been uttered

(adjective)

Accusative, masculine, plural of udgīrṇamantranicaya

udgīrṇamantranicaya - whose collection of mantras has been uttered

Compound type : bahuvrihi (udgīrṇa+mantranicaya)

• udgīrṇa – uttered, vomited forth, emitted
  adjective (masculine)
  Past Passive Participle
  Derived from `ud-√gṛ` (to utter, throw up).
  Prefix: ud
  Root: gṛ (class 6)
• mantranicaya – collection of mantras
  noun (masculine)

स्वाहाकारनिभस्वनान् (svāhākāranibhasvanān) - having sounds resembling the syllable "Svāhā"

(adjective)

Accusative, masculine, plural of svāhākāranibhasvana

svāhākāranibhasvana - whose sound resembles the cry Svāhā

Compound type : bahuvrihi (svāhākāra+nibhasvana)

• svāhākāra – the sound or utterance of 'Svāhā'
  noun (masculine)
• nibhasvana – resembling in sound, having a similar sound
  adjective (masculine)
  From `nibha` (resembling) + `svana` (sound).

अस्थिनैकतदिट्पुञ्जनीलमेघसमोपमान् (asthinaikatadiṭpuñjanīlameghasamopamān) - resembling many bone-white heaps of lightning and dark blue clouds

(adjective)

Accusative, masculine, plural of asthinaikatadiṭpuñjanīlameghasamopama

asthinaikatadiṭpuñjanīlameghasamopama - resembling many bone-white heaps of lightning and dark blue clouds

Compound type : bahuvrihi (asthina+naika+tadiṭpuñja+nīlamegha+samopama)

• asthina – bony, made of bone, bone-white
  adjective (masculine)
  Derived from `asthi` (bone).
• naika – many, not one
  adjective (masculine)
  A negative compound of `na` (not) + `eka` (one).
  Prefix: na
• tadiṭpuñja – heap/cluster of lightning
  noun (masculine)
• nīlamegha – dark blue cloud
  noun (masculine)
• samopama – comparable, resembling
  adjective (masculine)
  From `sama` (equal, similar) + `upama` (comparison).