淡定

dàndìng
  1. calm and collected
  2. unperturbed

CEDICT

  1. (neologism, slang) to calm down; to take it easy; to chill out
  2. calm and confident; poised
  3. to calm down; to take it easy; to chill out

Wiktionary

  1. 因看得開而冷靜、鎮定
  2. 沉著，平靜
  3. 穩重，穩健

維基詞典

Entry Composition

1 淡 dàn
  1. insipid
  2. diluted
  3. weak
  4. mild
  5. light in color
  6. tasteless
  7. indifferent
  8. (variant of 氮 dàn) nitrogen
2 定 dìng
  1. to fix; to set; to make definite
  2. to subscribe to (a newspaper etc); to book (tickets etc); to order (goods etc)
  3. to congeal; to coagulate
  4. (literary) definitely

Related entries

沉著 chénzhuó
  1. steady
  2. calm and collected
  3. not nervous
恬然 tiánrán
  1. unperturbed
  2. nonchalant
鎮定 zhèndìng
  1. calm
  2. unperturbed
  3. cool
「別擔心，」狄馬嘗試讓店員鎮定下來：「那不是我的血。」

"Don't worry," Dima attempted to put the woman at ease. "It's not mine."

Source: Tatoeba

滿不在乎 mǎnbùzàihu
  1. not in the least concerned (idiom)
  2. reckless
  3. couldn't give a damn about it
  4. unperturbed
  5. couldn't care less
  6. harum scarum