When you've absolutely had it with someone's bullshit and seriously couldn't care any less about what they do or say from here on out. Commonly felt among people who've been walked all over for most of their life.
girl: Hey I'm sorry I keep leading you on and getting involved with a bunch of other guys but I have a lot going on and I really don't know what I want right now so I was wondering if you'd give me another chance please?
guy: Look me straight in the eye, and tell me how DEAD SERIOUS I am when I tell you I don't give a fuck.
To not care or, "give a fuck" about a certain subject, object, action or comment.
Sally: "You look like an idiot"
Bob: "I don't give a fuck"
"Does it look like a give a fuck?"
"You really think I give a fuck?"
Willing to get a sexually transmitted disease.
When the girl licked my cock, I concluded that she dont give a fuck.