What is meant by a saturated solution? How can you prepare an unsaturated solution from a saturated one without adding more solvent?

A saturated solution is a solution that contains the maximum amount of solute that can be dissolved in a given amount of solvent at a specific temperature. No more solute can be dissolved in it at that temperature. To prepare an unsaturated solution from a saturated one without adding more solvent, you can increase the temperature of the saturated solution. 

As temperature generally increases, the solubility of most solid solutes in liquid solvents also increases, allowing more solute to dissolve and thus making the previously saturated solution unsaturated.