to take the cover off something hidden, so that it is now known: to reveal
Every use of this Aramaic verb in Daniel turns on a single picture: a covering comes away, and what was underneath is now in plain view. What gets uncovered is always a secret, and usually the specific secret of the dream Nebuchadnezzar refuses to describe, which his own advisers admit no one on earth can produce.
Daniel 2 presses that picture into a claim about God. The phrase "the one who uncovers secrets" is used of him three times in the chapter, so often that it works almost as a name, and the king finally repeats it back in Daniel 2:47. The claim is not that God is a good guesser. It is that the knowledge sits entirely on his side of the curtain and crosses over only if he lifts it.
That is why it matters that the same word can turn around, with the secret itself as the thing acted upon. When Daniel says the secret was uncovered to him, he immediately refuses the credit: it did not come from any wisdom of his own. The Aramaic keeps the giver and the receiver clearly apart, which is what gives the king's closing praise its edge. He calls God the uncoverer of secrets precisely because Daniel was able to uncover this one.
A companion word runs alongside it through the chapter, the Aramaic verb for knowing (יְדַע) in the sense of making something known. The two are not the same job: one lifts the cover, the other passes the news along.