Having a higher osmotic pressure than a comparison solution; -- of an aqueous solution. Increasing the concentration of dissolved solids increases the osmotic pressure, and thus the tonicity of a solution. Opposite of hypotonic and contrasting with isotonic. [PJC]
Having an osmotic pressure greater than that of blood plasma, which is approximately that of a 0.2 normal solution of sodium chloride. Cells taken from a medium of normal physiological osmolality and placed in a hypertonic medium will shrink. [PJC]
in a state of abnormally high tension; -- of muscle. [WordNet 1.5]