Meaning / usage: to not be convinced; not accepting or believing something as the truth.
Explaination : comes from a popular way of getting agreement, which is “buy in”. For example, a company director can say, “We need buy in from all all board members to proceed.” Therefore, if you “do not buy it, “then you are not agreeing.
1.Anne said she did not do it but I do don’t buy it.
2. My teacher did not buy My Story about the dog eating my homework.
3. The police would not buy his story.