A landmass is a very large body of land — big enough to think of as one piece on the map, such as a continent, or a huge island that stands on its own in the mind. Geography books love it. Eurasia is one landmass even though we split it into Europe and Asia; Africa is a landmass; Greenland is a huge landmass that is not usually called a continent. The word cares about the physical chunk of earth, not about countries or flags. Australia is both a continent and a landmass, which is why textbooks fuss over the difference. You would not call a farm, a park, or Taiwan a landmass in careful speech — too small. It is a calm, scientific-sounding word, not poetic. Mass here means a great bulk, not a church service, and not ‘the masses’ of people.