Disorganized means poorly planned or arranged, though it carries a pejorative connotation not seen in its close relative, unorganized, which simply means not organized (either in the sense of systematic arrangement or of labor unions). Thus disorganized generally only applies to people (e.g., the campaign was a disorganized mess), while unorganized can refer to people or inanimate objects (e.g., my desk is unorganized, but I am not).