Source : WordNet®

hypertonicity
     n 1: (of a solution) the extent to which a solution has a higher
          osmotic pressure than some other [ant: {hypotonicity}]
     2: (of muscular tissue) the state of being hypertonic [syn: {hypertonia},
         {hypertonus}] [ant: {hypotonia}, {hypotonia}, {hypotonia}]