trembling I. noun (-s) Etymology: Middle English, from gerund of tremblen to tremble : the action or condition of one that trembles: as a.: tremble II 3 b.: louping ill II. adjective Etymology: from present participle of tremble (I) : that trembles : shaking with or as if with fear or other emotion : fearful, vibrating, quaking • trem·bling·lyadverb • trem·bling·nessnoun-es