Crux/krʌks/ Definition 1 of 4Pro Tip 1/2Usage in Debate Use 'crux' to summarize or emphasize the main argument in discussions or debates. The crux of his argument was the need for more public parks. Pro Tip 2/2Emphasis on Importance 'Crux' signals that what follows is of utmost importance to the understanding of the whole issue. The crux here is public safety, not just aesthetics.