http://dictionary.cambridge.org/define.asp?key=care*3+4

http://dictionary.cambridge.org/define.asp?key=care*3+5

To gain a better understanding, here are a couple of examples from the Cambridge Dictionaries Online of the phrase "couldn't care less".


If someone "couldn't care less" about something, then that means it is of no concern to that person. It doesn't matter at all.

Similarly, we could also say: "That doesn't bother you in the least, does it?" = It doesn't bother you at all. - not even a little bit

"He's not bothered by that in the least." - He is not worried about it. It is of no concern to him.

similar - "He couldn't care less." That does not bother, worry or upset him.