किं तद्ब्रह्म किमध्यात्मं किं कर्म पुरुषोत्तम।अधिभूतं च किं प्रोक्तमधिदैवं किमुच्यते॥
kiṃ tad brahma kim adhyātmaṃ kiṃ karma puruṣottamaadhibhūtaṃ ca kiṃ proktam adhidaivaṃ kim ucyate
Word by word
The verse says
Arjuna said: What is that Brahman? What is the self? What is action? What is called the ground of matter, and what is called the ground of the gods?
In plain words
Krishna ended the last chapter with three technical words and walked straight past them.
Arjuna stops him. Five questions, no apology, no pretending.
He is about to fight a battle and he wants the words defined first.
Where you've felt this · at work
Halfway through a training session at work, everyone is nodding along. One person puts a hand up and says, sorry, what does that word actually mean. You can hear half the room exhale. They had all been nodding for twenty minutes, waiting for somebody else to go first.
Going deeper
Asking for a definition is treated here as a perfectly respectable spiritual act, and that is not true of every tradition.
Arjuna does not say he has understood. He does not nod and hope it clears up later. He lists the words he was given and asks what each one means, and nothing in the reply suggests he should have known already.
That sets a tone worth noticing. A teaching that cannot survive being asked plain questions is not being protected by anyone's silence. It is only being postponed.
So if you have been reading this book and quietly not understanding a third of it, you are in the position the book itself puts its student in. The questions in this verse are the ones you would have asked. Krishna answers them in the next two verses, quickly and without ceremony.