"De mark" is a term that means "to indicate, signify or set a boundary", and there are several synonyms that can be used interchangeably. Some examples include "boundary," "limit," "divide," and "delineate." Other potential synonyms include "demarcation," "outskirts," "perimeter," and "border." Each of these words carries its own nuanced meaning, with "border" referring specifically to a geographic boundary, and "limit" used to describe the furthest extent of something. Overall, using various synonyms for "de mark" can help add specificity and complexity to your writing, allowing you to more accurately convey your intended meaning.