What is "axled"

Usage examples of "axled".

There were other points of light that were in fact potato-shaped stony worldlets of various sizes, some carrying loads of instruments, the axled wheels of the old spacestation, the squares and rhomboids of advertising signs (hardly used now—they proved unpopular and counterproductive), high aircraft and spacecraft, and, higher still and parked in their plodding orbits, the old slowboats that had brought the original colonists.