The whole conference was totally disorganized - nobody knew what they were supposed to be doing.

disorganized 是由前缀 dis-（表示"否定、相反"）和 organized（"有组织的"）组成的形容词。dis- 否定 organized 的含义，所以 disorganized 意思是"无组织的、混乱的"。 organized 来自动词 organize（组织），加上 -ed 变成形容词，表示"被组织好的、有条理的"。