1. To be dressed and made up very attractively. Typically said of women. Wow, you look fit to kill—that dress is absolutely stunning on you! I felt pretty awful about myself after the breakup, but I decided that I was going to go out that night with my friends, and I would look fit to kill when I did.

2. To appear to be furious with or extremely annoyed by someone. She looked fit to kill Tom when he told her that he had burnt the dinner she'd spent all day preparing. Wow, the boss looked fit to kill that new intern just now—I wonder what she did wrong?