in a million years

1. In a very long time. Oh, wow, I haven't seen Andie in about a million years! How is she? Ugh, I haven't been on a vacation in a million years. Gosh, I haven't been back to my hometown in a million years. I wonder how much it's changed.

2. At any point in the future. Used in negative constructions to indicate something considered impossible. You expect those two political parties to work together on a solution to climate change? Ha, not in a million years! I never thought in a million years that I would actually win the lottery! He never thought in a million years that Samantha would ask him out, but he's very glad she did!