不得已

bùdéyǐ
  1. to act against one's will
  2. to have no alternative but to
  3. to have to
  4. to have no choice
  5. must

CEDICT

Entry Composition

1 不得 bùdé
  1. must not
  2. may not
  3. not to be allowed
  4. cannot
2 已 yǐ
  1. already
  2. to stop
  3. then
  4. afterwards