knock out
1．stun；render unconscious击昏
He received a blow on the head which knocked him out．他头上被打了一拳就昏倒了。
The falling ladder hit him on the head and knocked him out．梯子倒下来击中了他的头部，把他打昏过去了。
The boxer knocked his opponent out．拳击运动员把对手击晕。
2．eliminate from a competition；defeat an opponent by knocking him out of the fight 从比赛中排除
He was knocked out in the second round of this tournament．他在第2轮比赛中就被击败了。
He has now knocked out most of the other competitors．他现在已经压倒了多数其他竞赛对手。
3．empty by knocking 磕干净
After knocking out his pipe， the old man went on with his story．老人把烟斗里的烟灰磕干净后，又继续讲故事。
4．overwhelm with surprise使震惊；使惊得发呆
For a moment she was completely knocked out by the news．这条消息一下子就使她惊得目瞪口呆。
The beautiful scenery really knocks me out．这美丽的景色简直把我给迷住了。
5．play（a tune） rather unskillfully on the piano不熟练地弹钢琴
I am not a very accomplished pianist， but I can knock out a tune．我不是一个好的钢琴演奏者，但能勉强弹奏一曲。
6．create or finish roughly or hastily粗率地或匆忙地创作成或完成
He knocked out a plan in half an hour．他半小时就草拟出一个计划。
She knocked out ten letters in one evening．她一个晚上写了10封信。
7．make inoperative； destroy使不能使用；破坏；损坏
The telephone communications were knocked out by the storm．电话线被风暴摧毁了。
The power supply system knocked out by the typhoon has been repaired．被台风刮坏的供电系统已经修复。
8．make sb．exhausted使（某人）疲劳；使（某人）累垮
He knocked himself out with excessive work．他工作过度，把身体累垮了。
9．do one's best； exert oneself to the utmost尽最大努力；竭尽全力
He knocked himself out cramming for the exams．他正竭尽全力赶功课准备应试。
The workers knocked themselves out to fulfil their production quota ahead of time．工人们为提前完成生产指标，把全部气力都使上了。