द्यावापृथिव्योरिदमन्तरं हि व्याप्तं त्वयैकेन दिशश्च सर्वाः।दृष्ट्वाऽद्भुतं रूपमुग्रं तवेदं लोकत्रयं प्रव्यथितं महात्मन्॥
dyāv ā-pṛthivyor idam antaraṃ hivyāptaṃ tvayaikena diśaś ca sarvāḥdṛṣṭvādbhutaṃ rūpam ugraṃ tavedaṃloka-trayaṃ pravyathitaṃ mahātman
Word by word
The verse says
The space between earth and sky, and all directions, is filled by you alone. Seeing this astonishing, terrible form of yours, the three worlds are shaking, great one.
In plain words
Ugram — terrible, fierce. The word arrives here and does not leave.
Up to now the vision has been adbhuta, astonishing. Now both words are in the same line.
And it is not only Arjuna who is shaking. He says the three worlds are.
Where you've felt this · in community
A crowd in a stadium goes quiet all at once, before anybody has announced anything. You did not see what happened and you have no information. You are already standing up, because twenty thousand people around you have, and the quiet travels faster than the news does.
Going deeper
Fear becoming collective is the escalation in this verse, and it changes what Arjuna's reaction means.
So far his terror could be read as personal — a man out of his depth, which is understandable and says nothing about the thing itself. Here he reports that the worlds are trembling. Whether or not you take that literally, it moves the response from one person's nerves to a property of the encounter.
It is also the first hint that what he is seeing is not simply large. Size astonishes. Something else is producing the shaking, and he does not yet know what it is.
He will ask directly at verse 31, and the answer will explain everything in between. For now the chapter holds the reader in exactly the position Arjuna is in: aware that something is badly wrong with this magnificence, without being able to name it.