As for the appearance of the wheels and their construction: their appearance was like the gleaming of a chrysolite; and the four had the same likeness, their construction being as it were a wheel within a wheel. - Ezekiel 1:16
The phrase "wheels within wheels" is of ancient origin and has generally come to mean something that is not easily understood; that there is more to the situation than may appear on the surface. The quotation above, from the Old Testament
, is part of a mystifying biblical passage that has led many to believe he saw a UFO
The phrase denotes complexity, that one must look past the superficial to see deeper into a problem or situation. I know that you know, that I know that you know, that I..... Like the Russian matryoshka dolls we open one only to find another, and inside that yet another, etc., etc.
The phrase can also have a more sinister connotation, that there are ulterior motives behind seemingly innocuous actions - all part of a larger and less obvious plan.