महाभारतः mahābhārataḥ - book-8, chapter-14, verse-21

साश्वपत्तिद्विपरथं महाशस्त्रौघमप्लवम् ।
सहसा संतितीर्षन्तं पार्थं शस्त्रास्त्रसेतुना ॥२१॥

21. sāśvapattidviparathaṁ mahāśastraughamaplavam ,
sahasā saṁtitīrṣantaṁ pārthaṁ śastrāstrasetunā.

21. sa-aśva-patti-dvipa-ratham mahā-śastra-ogham aplavam
sahasā saṃtitīrṣantam pārtham śastra-astra-setunā

21. pārtham sahasā sāśvapattidviparatham aplavam
mahāśastraugham śastrāstrasetunā saṃtitīrṣantam

21. Arjuna, desiring to suddenly cross that great, boat-less flood of weapons—which was composed of horses, foot-soldiers, elephants, and chariots—by means of a bridge of weapons and missiles.

Words meanings summery:

• साश्वपत्तिद्विपरथम् (sāśvapattidviparatham) - composed of horses, foot-soldiers, elephants, and chariots (describing the enemy forces/weapons) (with horses, foot-soldiers, elephants, and chariots)

• महाशस्त्रौघम् (mahāśastraugham) - great flood of weapons (great flood/torrent of weapons)

• अप्लवम् (aplavam) - boat-less, un-navigable (without a boat, un-navigable)

• सहसा (sahasā) - suddenly, forcefully (suddenly, forcibly, impetuously)

• संतितीर्षन्तम् (saṁtitīrṣantam) - desiring to cross (it) (desiring to cross over)

• पार्थम् (pārtham) - Arjuna (Arjuna (son of Pṛthā/Kuntī))

• शस्त्रास्त्रसेतुना (śastrāstrasetunā) - by means of a bridge of (his own) weapons and missiles (by a bridge of weapons and missiles)

Words meanings and morphology

साश्वपत्तिद्विपरथम् (sāśvapattidviparatham) - composed of horses, foot-soldiers, elephants, and chariots (describing the enemy forces/weapons) (with horses, foot-soldiers, elephants, and chariots)

(adjective)

Accusative, neuter, singular of sāśvapattidviparatha

sāśvapattidviparatha - with horses, foot-soldiers, elephants, and chariots

Compound type : bahuvrīhi (sa+aśva+patti+dvipa+ratha)

• sa – with, together with
  indeclinable
• aśva – horse
  noun (masculine)
• patti – foot-soldier, infantry
  noun (masculine)
  Root: pat (class 1)
• dvipa – elephant (lit. 'drinker twice')
  noun (masculine)
• ratha – chariot, car
  noun (masculine)

Note: Refers to the characteristics of the enemy forces forming the "flood of weapons."

महाशस्त्रौघम् (mahāśastraugham) - great flood of weapons (great flood/torrent of weapons)

(noun)

Accusative, masculine, singular of mahāśastraugha

mahāśastraugha - great flood of weapons

Compound type : karmadhāraya (mahā+śastra+ogha)

• mahā – great, large, mighty
  adjective (feminine)
• śastra – weapon (thrown by hand or wielded), implement
  noun (neuter)
  Root: śas (class 1)
• ogha – flood, torrent, stream, multitude
  noun (masculine)

Note: Accusative singular, direct object of saṃtitīrṣantam.

अप्लवम् (aplavam) - boat-less, un-navigable (without a boat, un-navigable)

(adjective)

Accusative, masculine, singular of aplava

aplava - without a boat, having no boat, impossible to cross (by boat)

Formed with negative prefix a- and plava (boat).

Compound type : bahuvrīhi (a+plava)

• a – not, un-
  indeclinable
• plava – boat, raft, swimming, floating
  noun (masculine)
  From root plu (to float/swim).
  Root: plu (class 1)

Note: Refers to the difficulty of crossing the "flood of weapons."

सहसा (sahasā) - suddenly, forcefully (suddenly, forcibly, impetuously)

(indeclinable)

Instrumental of sahasa (force, power) used adverbially.

Root: sah (class 1)

संतितीर्षन्तम् (saṁtitīrṣantam) - desiring to cross (it) (desiring to cross over)

(adjective)

Accusative, masculine, singular of saṃtitīrṣant

saṁtitīrṣant - wishing to cross over, desiring to traverse

Desiderative Present Active Participle

From desiderative stem of root tṛ (to cross) with prefix sam-.

Prefix: sam

Root: tṛ (class 1)

पार्थम् (pārtham) - Arjuna (Arjuna (son of Pṛthā/Kuntī))

(proper noun)

Accusative, masculine, singular of pārtha

pārtha - son of Pṛthā (Kuntī), Arjuna

Derived from pṛthā (Kuntī, Arjuna's mother).

Note: Object of implied verb (or saṃtitīrṣantam refers to him).

शस्त्रास्त्रसेतुना (śastrāstrasetunā) - by means of a bridge of (his own) weapons and missiles (by a bridge of weapons and missiles)

(noun)

Instrumental, masculine, singular of śastrāstrasetu

śastrāstrasetu - bridge of weapons and missiles

Compound type : tatpuruṣa (śastra+astra+setu)

• śastra – weapon (wielded, e.g., sword), implement
  noun (neuter)
  Root: śas (class 1)
• astra – missile, projectile weapon (thrown/discharged)
  noun (neuter)
  Root: as (class 4)
• setu – bridge, dam, barrier
  noun (masculine)
  Root: si (class 5)

Note: Instrument of crossing.