tremor

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A shaking or vibrating movement, as of the earth.
2. n. A trembling or quivering effect: a tremor of aspen leaves.
3. n. An involuntary trembling or quivering, as from nervous agitation or weakness.
4. n. A nervous quiver or thrill: felt a tremor of joy.
5. n. A state or feeling of nervous agitation or tension.
6. n. A tremulous sound; a quaver.

Century Dictionary and Cyclopedia

1. n. In colonial furniture, a sort of hood or head-piece found on high cupboards and the like: probably derived from a French type.
2. n. A shaking or quivering caused by some external impulse; a close succession of short vibratory or modulatory movements; a state of trembling in a living object or substance: as, the tremor of the aspen-leaf.
3. n. An involuntary or convulsive muscular shaking, quaking, or quivering, as from weakness, disorder, or emotion.
4. n. A trembling, quivering, or quavering quality or effect: as, a tremor of light.
5. n. Synonyms Trepidation, Emotion, etc. (see agitation), quiver, quivering, quaking. See trepidation.

Wiktionary

1. n. A shake, quiver, or vibration.
2. n. An earthquake.
3. v. To shake or quiver excessively and rapidly or involuntarily; to tremble.

GNU Webster's 1913

1. n. A trembling; a shivering or shaking; a quivering or vibratory motion.

WordNet 3.0

1. n. an involuntary vibration (as if from illness or fear)
2. v. shake with seismic vibrations
3. n. shaking or trembling (usually resulting from weakness or stress or disease)
4. n. a small earthquake