From Longman Dictionary of Contemporary Englishharnesshar‧ness1 /ˈhɑːnəs $ ˈhɑːr-/ noun [countable, uncountable] 1 TTBa set of leather bands used to control a horse or to attach it to a vehicle it is pulling2 
TDa set of bands used to hold someone in a place or to stop them from falling a safety harness3 → in harness4 → in harness (with somebody)
TDa set of bands used to hold someone in a place or to stop them from falling a safety harness3 → in harness4 → in harness (with somebody)Examples from the Corpus
harness• An essential piece of rock-climbing equipment is a climbing harness.• To wait in heavy harness On fluttered folk and wild Your new-caught, sullen peoples, Half devil and half child.• Taking one hand off the wheel, Nathan reached out and hooked his fingers through the front of her harness.• The sound of a horse in harness, of its hoof idly striking a stone!• So with borrowed gear, no harness and a stranger I set off.• Playpens or other harnesses, for instance, may be used frequently to keep their chil-dren safe.• The karabiner must be correctly attached to the harness.harnessharness2 verb [transitive] 1 CONTROLto control and use the natural force or power of something We can harness the power of the wind to generate electricity.2 TTBto fasten two animals together, or to fasten an animal to something using a harness3 TTBto put a harness on a horse→ See Verb tableExamples from the Corpus
harness• The Missouri River is harnessed for hydroelectric power.• We harness fossil energy and breathe life into machines.• The important thing is to harness growth to self-knowledge, a ready acceptance of change, swift-moving business practice and sound judgement.• The snag is - first you must harness the fish.• A mixture of envy and admiration once led fishermen to try to harness the heron's gifts.• Attempts to harness the numerical strength of the casual poor had foundered on the rocks of seeming apathy.• It is designed for maximum pleasure and harnesses the power of a System Porsche 1.2 fuel-injected engine, complete with three-way catalyser.• They also featured coaches that could harness their players' egos.• A hybrid type of society emerged, in which archaic social forces were harnessed to modern industrial techniques.From Longman Business Dictionaryharnesshar‧ness /ˈhɑːnəsˈhɑːr-/ verb [transitive] to control and use a natural force or people’s energy or skillsHe designs systems to harness the energy of waves to produce electricity.→ See Verb tableOrigin harness1 (1200-1300) Old French herneis “bags, equipment” 