Use 'unorganized' to describe events that seem to happen without preparation or structure. Everyone just showed up, and it turned into an unorganized party.
Pro Tip 2/3
Unproductive Outcomes
Describe outcomes that suffered due to a lack of organization with 'unorganized'. Their unorganized project yielded poor results.
Pro Tip 3/3
Describing Noise
'Unorganized' can convey the sense of noise or talking that is not coherent or orderly. The classroom discussion was so unorganized that I couldn't understand the main point.