n. [ Pref. hyper- + tonic. ] (Physiology, Biochemistry) 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. [ wns=1 ] [ PJC ]

A knowledge of the colligative properties of solutions . . . is essential for one to understand fully the principles involved in rendering intravenous solutions isotonic with blood serum, or opthalmic solutions isotonic with lachrymal fluid. Solutions thus adjusted produce less shock and much less irritation than those which are hypotonic or hypertonic, and present-day practise recognizes the desirability of making the necessary adjustments whenever possible. Cook & Martin (Remington's Practice of Pharmacy, Tenth Ed.: Mack Publ., Easton Pa., 1951)

2. Specifically: 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. [ wns=1 ] [ PJC ]

3. in a state of abnormally high tension; -- of muscle. [ wns=2 ]
Syn. -- pumped-up. [ WordNet 1.5 ]

a. [ See Hyper-, and Tonic. ] See Vasoconstrictor. [ 1913 Webster ]