A phrase meaning "The degree to which I care about this could not possibly go lower." Most people naturally interpret it to mean "I care about this as
little as any human could; my degree of care is 0".
But it can also be interpreted to mean "I care about this to a certain extent (which may be a little or a whole lot) and there is no way in
hell my caring is ever going to drop."
Arguments about this can get
pretty heated, with Team Couldn't Care Less tending to care more.
"Guess what happened on Dancing with the Stars last night?"
"Please don't bother me with that, I really couldn't care less about it."
"Mr.
Politician, do you care about America?"
"I'm glad you asked that. I care about America more than
anything in the world, and I couldn't care less, not in a million years. You'll have to pry my care from my
cold dead hands."