adjective Being without definite character or nature.
adjective Lacking organization or unity.
adjective In the non-crystalline solid state of, or being a non-crystalline counterpart to, a crystalline solid.
Glass is an amorphous solid, but some glass is called "crystal" because it looks crystalline and has been called crystal since before humans even understood molecular structure at all.
adjective Infinite and not the disjoint union of two infinite subsets.