Antonyms of adj conscientious

2 senses of conscientious

Sense 1
conscientious, painstaking, scrupulous -- (characterized by extreme care and great effort; "conscientious application to the work at hand"; "painstaking research"; "scrupulous attention to details")

INDIRECT (VIA careful) -> careless -- (marked by lack of attention or consideration or forethought or thoroughness; not careful; "careless about her clothes"; "forgotten by some careless person"; "a careless housekeeper"; "careless proofreading"; "it was a careless mistake"; "hurt by a careless remark")

Sense 2
conscientious (vs. unconscientious) -- (guided by or in accordance with conscience or sense of right and wrong; "a conscientious decision to speak out about injustice")

unconscientious (vs. conscientious) -- (not conscientious;)
        => conscienceless, unconscionable -- (lacking a conscience; "a conscienceless villain"; "brash, unprincipled, and conscienceless"; "an unconscionable liar")

Similarity of adj conscientious

2 senses of conscientious

Sense 1
conscientious, painstaking, scrupulous -- (characterized by extreme care and great effort; "conscientious application to the work at hand"; "painstaking research"; "scrupulous attention to details")
       => careful (vs. careless) -- (exercising caution or showing care or attention; "they were careful when crossing the busy street"; "be careful to keep her shoes clean"; "did very careful research"; "careful art restorers"; "careful of the rights of others"; "careful about one's behavior")

Sense 2
conscientious (vs. unconscientious) -- (guided by or in accordance with conscience or sense of right and wrong; "a conscientious decision to speak out about injustice")