Unless I am thinking backwards, hypertonic refers to a high concentration of particles in a solution. This means that water would diffuse out of a cell to create equilibrium, possibly causing it to plasmolize (shrivel up.) For example, salt water is hypertonic to most cells, so when they are placed in a salt solution, they shrivel up. If the solution is hypotonic, meaning it has a low concentration of particles, that water will diffuse into cells, possibly causing them to burst.
