trembling
     adj : vibrating slightly and irregularly; as e.g. with fear or
           cold or like the leaves of an aspen in a breeze; "a
           quaking bog"; "the quaking child asked for more";
           "quivering leaves of a poplar tree"; "with shaking
           knees"; "seemed shaky on her feet"; "sparkling light
           from the shivering crystals of the chandelier";
           "trembling hands" [syn: {quaking}, {quivering}, {shaking},
            {shaky}, {shivering}]
     n : a shaky motion; "the shaking of his fingers as he lit his
         pipe" [syn: {shaking}, {shakiness}, {quiver}, {quivering},
          {vibration}, {palpitation}]
Source: WordNet® 2.0