Mass Tourism is the wide-scale Travel by a large number of people from all walks of life, brought about by the increase in discretionary income, leisure time, and reliable and inexpensive modes of transportation such as the car and plane.
Other definition:
Mass tourism is the traditional, large scale tourism commonly, but loosely used to refer to popular forms of leisure tourism pioneered in southern Europe, the Caribbean, and North America in the 1960s and 1970s.