疑難

疑难
yínán
  1. hard to understand
  2. difficult to deal with
  3. knotty
  4. complicated

CEDICT

Entry Composition

1 疑 yí (bound form) to doubt; to suspect
2 難 nán
  1. difficult (to...)
  2. problem
  3. difficulty
  4. difficult
  5. not good