• alāta-cakra — a whirling firebrand
  Contiguous join (alāta + cakra) from synonyms. Classical Indian image for illusory continuity — used in Māṇḍūkya-kārikā and the Yoga-vāsiṣṭha. Bhāgavatam appropriates it here for a flying asuric city: saṁsāra wearing iron.
• bhrāmyat — wandering
  Present participle of √bhram — to whirl, to be deluded. Same root as bhrama (error). The asura's vehicle and the asura's mind share one verb: both whirl.
• duravasthitam — never remaining in one place
  duḥ + ava + √sthā. Hard to stay-put. The whole asuric career is duravasthita; only the devotee's heart rests in Kṛṣṇa's lotus feet — su-avasthita.
• vyomni — in the sky
  Locative of vyoman. The Upaniṣads use vyoman for the supreme space; Bhāgavatam often distinguishes bhautika-vyoman (material sky) from cid-vyoman (Vaikuṇṭha). Saubha rides bhautika-vyoman only.
• kvacit — at one moment
  Indefinite adverb of location/time. Repeated four times in this short verse — the very rhythm enacts Saubha's restlessness. Bhāgavata prosody often performs its subject.

Like a torch whirled in the dark — alāta-cakra — that draws a circle which is no real circle but only the persistence of one fire's motion, Saubha appears as multiple cities at once. The Vedānta uses the very same image (alāta-cakra-vat) for saṁsāra itself: motion mistaken for substance.