So for example, "Jen polished off her dinner." It means she ate all of her dinner. There's not even a crumb. She ate everything. She polished off her dinner. You can also use "polished off" with drinks, too. Imagine if somebody loves wine and they drink the whole bottle, okay? "They polished off the wine." There's no more wine left. So that means there's none left because you ate or drank it all.