n.

1. 挑戰；邀請比賽[C][+to-v]
   He received a challenge to a TV debate.

   他接到電視辯論的挑戰。

2. 質疑；指責；異議[C]
3. 頗有作為的工作；艱鉅的事[C]
   To build a road in the mountainous area was a real challenge.

   在山區修築公路確是艱鉅的事。

   He wants a career that offers a challenge.

   他要有挑戰性，能有一番作為的事業。

4. （哨兵，警衛等）查問口令；盤問[C]
   I was met with a challenge when approaching the post.

   我在走近哨所時被查問身分。

5. 【律】（對某陪審員出庭等表示的）反對[C]
6. 有挑戰性[U]

vt.

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

   我要他拿出證據。

2. 對……提出異議；懷疑；反對
   He challenged my view on that matter.

   他就我對那件事的看法提出異議。

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

   那個新職位激發他在業餘時間更加努力學習。

   The event challenges an explanation.

   那個事件需要解釋。

4. （哨兵，警衛等）查問；盤問
5. 【律】宣布反對（某陪審員等）

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.