• pāṣaṇḍinām — of the atheists
  Genitive plural of pāṣaṇḍī. The same word as in v. 8 but now in agentive form. The pāṣaṇḍas are not just doctrines but persons; the Bhāgavatam is realistic about who breaks the dikes.
• asat-vādaiḥ — by false arguments
  Compound: asat (unreal, false) + vāda (argument). Gauḍīyas use sat-vāda for any argument that converges on Kṛṣṇa as Bhagavān; asat-vāda is its opposite. The criterion is not eloquence but conclusion.
• veda-mārgāḥ — paths of the Veda
  Compound: Veda + mārga (path). The varṇa-āśrama-prescriptions, the sacrificial paths, ultimately culminating in bhakti. Gauḍīyas treasure the Veda's paths as the natural staircase to Kṛṣṇa-prema.
• setavaḥ — dikes, boundaries
  Setu — the same word used for Rāma's setu to Laṅkā. Boundaries are sacred in Vedic culture (cf. Manu's metaphors). To break a setu is a serious crime — physical, social, or hermeneutic.
• kalau — in Kali (age)
  Locative. The age explicitly named in a verse about the rainy season — the poet uses every device to remind us that varṣā is also Kali in micro.

When Indra rains hard, even the strongest dikes give way — and in Kali, pāṣaṇḍa-arguments break the dikes of Vedic injunction. The verse is bleak about the present age. Mahāprabhu's answer is to rebuild the dikes higher with nāma-saṅkīrtana — a project that does not depend on the dikes' brittle mud.