n.

1. 挑战；邀请比赛[C][+to-v]
   He received a challenge to a TV debate.

   他接到电视辩论的挑战。

2. 质疑；指责；异议[C]
3. 颇有作为的工作；艰巨的事[C]
   To build a road in the mountainous area was a real challenge.

   在山区修筑公路确是艰巨的事。

   He wants a career that offers a challenge.

   他要有挑战性，能有一番作为的事业。

4. （哨兵，警卫等）查问口令；盘问[C]
   I was met with a challenge when approaching the post.

   我在走近哨所时被查问身份。

5. 【律】（对某陪审员出庭等表示的）反对[C]
6. 有挑战性[U]

vt.

1. 向……挑战[（+to）][O2]
   I challenged him to show his proof.

   我要他拿出证据。

2. 对……提出异议；怀疑；反对
   He challenged my view on that matter.

   他就我对那件事的看法提出异议。

3. 要求，需要；刺激，激发[O2]
   The new position challenged him to study still harder during his spare time.

   那个新职位激发他在业余时间更加努力学习。

   The event challenges an explanation.

   那个事件需要解释。

4. （哨兵，警卫等）查问；盘问
5. 【律】宣布反对（某陪审员等）

n.

1. a call to someone to participate in a contest or fight to decide who is superior.
   ▸a demanding task or situation.
   ▸an attempt to win a sporting contest.
2. a call to prove or justify something.
3. Medicine  exposure of the immune system to pathogenic organisms or antigens.

v.

1. dispute the truth or validity of.
   ▸Law  object to (a jury member).
   ▸(of a guard) order (someone) to prove their identity.
2. invite (someone) to engage in a contest or fight.
   ▸make a rival claim to (a position).
   ▸ [usu. as adj. challenging] test the abilities of.
3. Medicine  expose (the immune system) to pathogenic organisms or antigens.