The word "neaten" refers to make something clean and tidy, but if we talk about its antonyms, then the opposite of the word neaten is to make something messy or untidy. Some of the antonyms of neaten are dirty, disheveled, disorderly, unkempt, cluttered, chaotic, and disordered. For instance, the children were asked to neaten their room, but they made it more disorganized and unclean by scattering their toys and books all over the room. So, in such a situation, the opposite of neaten is applicable. The use of antonyms of words helps us to understand the context of the situation in a better way.