If a cell containing 2% salt is placed into an 18% salt solution, intracellular fluid will leave the cell, due to the osmotic pressure differential, and enter the solution. As a result, the cell will shrink and shrivel (and ultimately die). With respect to the cell (which for discussion purposes will be called isotonic), the 18% salt solution is hypertonic.
In humans, the cells, tissues and blood have a concentration of solutes equivalent to 0.9% saline (salt solution). So in the medical world, the term “isotonic” refers to solutions such as IV fluids that have 0.9% salinity. Compared to human cells, the cell in your question would be hypertonic, having 2% salt compared to 0.9%. The solution in your question would also be hypertonic, even more so than the cell.
In summary, “isotonic” means having the normal, physiologic salt content of the species under consideration. “Hypertonic” means having a higher salt concentration, “hypotonic”, lower.
Cells exposed to hypotonic fluid swell and burst. Cells exposed to hypertonic fluid shrivel and shrink.