短语 to bite the hand that feeds 的字面意思是“咬了喂食人的手”，实际意思是“恩将仇报、忘恩负义”。这个短语常用来描述某人对曾经帮助过他的人或组织作出不友善的举动。
Talk about biting the hand that feeds you. As soon as he finished his training he left the company and joined a competitor.
Teenagers are often rebellious and bite the hands that feed them. When I was in my teens I was very rude to my parents even though they gave me everything.
另一个含有 hand 的短语是 to bite someone's hand off “一口把人的手给咬下来了”。听着很害怕，但实际上这个短语是用来形容“迫不及待地、毫不犹豫地答应一件事情或接受一个条件”，因为这件事情或条件实在是太好了。
I nearly bit his hand off when he offered me the concert tickets. I’d been trying for ages to get some.
“What would you say if I offered you the job in Beijing?”
“I’d bite your hand off!”