The antonyms for the word "are conscientious" could include careless, irresponsible, neglectful, thoughtless, and lazy. These words describe individuals who lack the diligence and attention to detail associated with being conscientious. Someone who is careless, for example, might overlook important details or fail to take responsibility for their actions. An irresponsible person might shirk their duties and fail to meet their obligations. Neglectful people might fail to perform necessary tasks or make important decisions. Thoughtless individuals might act impulsively or fail to consider the consequences of their actions. Lazy people might lack motivation or fail to put in the necessary effort to succeed.