shudder
     n 1: an almost pleasurable sensation of fright; "a frisson of
          surprise shot through him" [syn: {frisson}, {shiver}, {chill},
           {quiver}, {thrill}, {tingle}]
     2: an involuntary vibration (as if from illness or fear) [syn:
        {tremor}]
     v 1: shake, as from cold; "The children are shivering--turn on
          the heat!" [syn: {shiver}]
     2: tremble convulsively, as from fear or excitement [syn: {shiver},
         {throb}, {thrill}]
Source: WordNet® 2.0