掉以轻心 (掉以輕心) diào yǐ qīng xīn

diào yǐ qīng xīn set phrase to treat with little regard; to be complacent
Domain: Idiom 成语
Notes: (CC-CEDICT '掉以輕心'; CCI '掉以轻心', p. 112; Guoyu '掉以輕心')