When it comes to describing the concept of "thick space," there are a number of synonyms that can be used to help convey its meaning. Some of the top options include terms like dense space, substantial space, and solid space. All of these terms refer to a space that has a greater sense of weight, depth, and physical presence than a more typical, airy space. Other possibilities might include phrases like heavily packed space, crowded space, or tightly filled space, which emphasize the sense of compression that often characterizes thick spaces. Ultimately, the choice of synonym will depend on the specific context in which it is being used.