指某情况是之前没有预想到的to be surprised by the turn of events

• 原策划的谈话会发展成了辩论会，这是记者也始料未及的。

  What was originally planned as a discussion developed into a debate. Even the reporter did not expect this.

• 令他始料未及的是，可爱的儿子突然得了白血病。

  What he had not expected was that his cute son would suddenly develop leukaemia.