Merriam-Webster Collegiate Dictionary - tremor

 noun  Etymology: Middle English tremour, from Anglo-French ~, from Latin, from tremere  Date: 14th century  1.  a. a trembling or shaking usually from physical weakness, emotional stress, or disease  b. nervous excitement the exhibit caused a ~ in the artistic community  2. a quivering or vibratory motion; especially a discrete small movement following or preceding a major seismic event  3.  a. a feeling of uncertainty or insecurity a ~ of hesitation  b. a cause of such a feeling