这句话的意思是「我不在乎」，「缺乏兴趣」(lack of interest)，也就是：I don""t care at all.或I don't give a hoot.例如：
人家如果问：What do you think of the budget-cut?(你对预算削减有何看法?)
你回答：I couldn't care less.(我毫不在乎)
How do you like Mr. Lee's political point of view?(你喜欢李先生的政见吗?)
I couldn't care less.(我才不在乎呢!)
但是有时说话者也有「口是心非」：例如：
I couldn't care less about the promotion or pay raise.(我不在乎升级或加薪)
而实际上他是根本在乎升级和加薪的，那么人家也许就会回答说：Yes, you do(care).
至于I couldn't care more.就是「我很在乎」(I care a lot.)或I care deeply.同理：
I couldn't agree more.=I totally agree.(我完全同意)
I couldn't please you more.=I did my best to please you.(我尽量使你高兴)
I couldn't be more right.=I am totally right.
但是老外为了「自尊」，不愿强调自己的错误，所以很少人说：
I couldn't be more wrong.
注意：一般人都用否定句，但也有老外把肯定句与否定句互用。
不过，严格来说，I could care less. = I care to some degree.(care的程度可能减少)
I could care more.=I care some.(care的程度也许增加)(主词可用任何人称代名词：he, she, you, we, they等。但只用could，不用can。)
2. No bones about it.
意思是：真实的，诚恳的(truly, sincerely or exactly)，也就是to make no bones about it.(bone要加s, it是指something)例如：
His wife is beautiful;no bones about it.(他的太太真是很漂亮)
Mr. A made no bones about it when he talked about abortion issue.(当A先生谈到堕胎问题时，他是诚恳的。)
When I spoke on the topic,he said, "No bones about it."(也就是他同意我的看法)
No bones about it;the weather is very chilly today.(今天是真的太冷了)
