Charlie Sheen tells TMZ ... he's teaching his 2-year-old twin boys new words this weekend -- like "rehab" -- because he wants them to know where their mother spends so much time.
Charlie tells TMZ ... it's the first time he's been able to spend a weekend with Bob and Max since the judge took custody away from him back in March.
Charlie says he's spending the weekend expanding the boys' vocabulary: "I am teaching them words, because they're speaking now. I'm teaching them the word 'rehab' so they always know where their mom is."
Charlie has settled his custody dispute with Brooke Mueller, but it sound like it's still game on.