Mountaineering is very popular outdoor activity in Taiwan. Taiwan is a famous mountain island, especially being a lot of high mountains, and the development of economics growth, political free and social welfare is very high. Many types of mountaineering activities, including trekking, hiking, backpacking, tramp, even climbing that need high technical knowledge, skills and equipments, may take and practice in Taiwan mountains, and the attractions formed by tourism and recreation resources pull many foreign visitors. But, what is mountaineering? What is the definition of mountaineering? What is the origin and nature of mountaineering?The answer may not be given, because of having been hardly found from mountain literatures in Taiwan. Recently, many works concerned with mountaineering, for example: mountaineering education, mountaineering school and so on, have expanded and created, but those are not quite successful. The reasons are about the nature which the definition and essence of mountaineering is not clear and chaos. Another reason is that which is the best translation of mountaineering in Chinese? (mountaineering (登山), mountaineering sport (登山運動), or mountaineering activity (登山活動)?) The methods of this study are through the collection of literatures available in Taiwan, and comparison between the thesis of master or doctor and the papers of mountaineering conferences. The results reveal that the best translation of mountaineering in Chinese is "登山"(mountaineering). There are two kinds of definitions, one is mountains climbing that need high technical knowledge, skills, equipments and the ability of sports, the other is close to mountains and engaging in any sport, recreation and travel activity. Recently, the content of mountaineering takes tourism geography into account, in consequence the situation that the essence of mountaineering has been modified into three parts: landscape resource, mountaineering sport, and ecotourism, has been emerged.