Travel to natural places — rain forests, coral reefs, mountains, wetlands — done in a way that tries not to damage them. It usually means small groups, local guides, staying in simple places owned by local people, and learning about the plants, animals and the people who live there. The idea has two halves, and both matter: the place should not be hurt, and the money should stay with the people who live there. Also used for the industry itself: the companies, tours and hotels that sell these trips. In real use the word is stretched a lot. Any hotel with a garden and a sign asking you to reuse your towel may call itself 'ecotourism', so people sometimes say it with a raised eyebrow, and there is a common word 'greenwashing' for calling something eco when it is not. It is a fairly formal, written word — you meet it in travel articles, government plans and school textbooks more than in everyday talk. Uncountable: no 'an ecotourism', no plural.