hill to die on

1. An issue or course of action that one pursues with total and wholehearted conviction, despite the difficulty and potential consequences of doing so. It's clear that the senator and her party are making this tax hike a hill to die on. We'll see how voters feel about it during the next election. Look, having principles in business is important, but not if they're going to destroy your company. This is not a hill to die on! Do you know how many single issue voters there are? For them, this is a hill to die on!

2. A position or argument that one maintains with total conviction, without concern as to whether or not one will be considered correct or change anyone else's opinion. Often used facetiously. I know it's a dumb hill to die on, but I don't care what anyone says—the third film is the best in the entire series! You got into a fight with him over the correct way to organize utensils in the kitchen? Is that really a hill to die on? I don't understand why this is a hill to die on. OK, so your sister doesn't like that video game—so what?