Harness/ˈhɑːrnɪs/ Definition 1 of 4Pro Tip 1/2Safety Device Remember 'harness' as a protective measure to prevent accidents. Always use a harness when rock climbing. Pro Tip 2/2Not Just for Humans 'Harness' can be for pets or objects to secure them in place too. She put a harness on her camera to stabilize it.