According to most people, a stupid phrase that means the opposite of what's intended.

According to a few people, a sarcastic way to say you really couldn't care less.

Probably what was originally intended is a phrase like "I could give a shit," just a little more subtle than "I don't give a shit." Or "I could give a damn." So they could care less, but they still don't care.

Wrong slang. It's supposed to be "I couldn't care less" - because I have no interest. "I could care less" means there is some interest.

an expression that idiots use when they don't care about something or have no interest in something. what they really mean is "i couldn't care less"

This is what stupid people say when they, in fact, mean, "I couldn't care less." The intent of the phrase is to express the fact that the level of caring the user has is nil. However when taken literally, the phrase dictates that there is at least some level of caring and it is possible to care less. Some people have said that the phrase is used sarcastically and that people who use it know that the meaning is opposite to the literal interpretation. However it is far more likely that people who say, "I could care less," and mean the opposite are just stupid.

1. It is possible for me to be less interested in the subject than I am at this moment.
2. It is not possible for me to be less interested in the subject than I am at this moment.

When unsure as to which definition should be applied, it can help to judge the person's intelligence - morons usually mean #2.

"I could care less" reminds the listener of your human compassion as an American. You are essentially telling him or her, "as you can tell from my clearly stated opinion, I do not care very much at all about this subject I am referring to. However, let us never forget that--if I wanted to--I could care even less." As we are sometimes prone to speak in hyperbole, e.g. "people who park crooked like that should be disembowelled and set on fire" (when a jail term would obviously suffice, given the spectre of rape), "I could care less" is an institutional phrase that compels us to remember our power must be tempered with mercy, which is expressed in the form of restrained indifference. Just as there is no real limit to justice/revenge beyond the constructs of liberal rhetoric, apathy is an abyss that must be skirted prudently. Without care, one could, without realizing it, become so indifferent to a subject that he or she neglects to even opine about it. On a large scale, this would threaten the core dynamic of what it is to be American: the unstoppable force of limitless guidance checked only by the immovable object of absolute unreceptivity to the guidance of others. "I could care less" is an enshrinement of self-discipline.

A way of checking on whether or not the person you're talking to is a fussy-prissy sort of person, or can actually pick up on sarcasm.