Antonyms for the word "methodicalness" include disorganized, haphazard, messy, incoherent, erratic, random, and chaotic. These words describe a lack of structure and organization, the opposite of methodicalness. Disorganized implies a lack of planning or order, while haphazard describes something that is done without much thought or system. Messy implies a lack of neatness, and incoherent describes something that is not clear or logical. Erratic suggests unpredictability and inconsistency, and random means something that is chosen by chance or without any purpose. Chaotic implies a complete lack of order or control.