careless  
adjective uk/ˈkeə.ləs/ us/ˈker.ləs/
  (NO ATTENTION)      
 B1 不小心的;粗心的,马虎的
not taking or showing enough care and attention
  My son's teacher says that his work is often rather careless. 我儿子的老师说他做作业经常粗心大意。 
 He made a careless remark (= one made without thinking) about her appearance that really upset her. 他对她外貌的一句随意的评价让她很不快。 
 - More examples
 - I tackled him about his careless work and frequent absences.
 - He's very careless with his money.
 - His work is full of careless mistakes.
 - She didn't mean to damage the painting, but she was too careless with it.
 - She's rather careless about her appearance.
 
  (NO WORRY)      
 literary不经意的,无忧无虑的 
relaxed, natural, and free from worry
 See also: carefree