A subcontinent is a part of a continent. It is formed of a various number of sims and can also be divided into regions or subcontinents. A subcontinent is too small or uncomplete separated from a larger continent to be considered itself a continent. There is no way to define clear borders for a subcontinent. For example, somebody might consider Bay City a subcontinent of Sansara. It is true, but someone else might include in Bay City the suburbs (Nova Albilon, Luna and Shemerville). A subcontinent might be considered all the South part of Sansara, with its large plateaus, but this means that Snowlands, another subcontinent, will be split in two.
This creates confussions for Geographs, but it is much better to avoid fixing too many barriers and let everybody divide land as it is better for the moment.