不知

bùzhī
  1. not to know
  2. unaware
  3. unknowingly
  4. fig. not to admit (defeat, hardships, tiredness etc)

CEDICT

Entry Composition

1 不 bù
  1. no; not so
  2. (bound form) not; un-
2 知 zhī
  1. to know
  2. to be aware