What is dnf?

Some articles on dnf:

Rinaldo Capello - Racing Record - Complete 24 Hours of Le Mans Results
1998 Gulf Team Davidoff GTC Competition Thomas Bscher Emanuele Pirro McLaren F1 GTR GT1 228 DNF DNF 1999 Audi Sport Team Joest Michele Alboreto Laurent Aïello Audi R8R LMP 346 4th 3rd 2000 Audi ...