undulation

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A regular rising and falling or movement to alternating sides; movement in waves.
2. n. A wavelike form, outline, or appearance.
3. n. One of a series of waves or wavelike segments.

Century Dictionary and Cyclopedia

1. n. In playing musical instruments of the viol class, the wavy tone produced by oscillating or balancing the finger on a string that is being stopped.
2. n. The act of undulating; a waving motion; fluctuation; in physics, wave-motion: as, the undulations of water or air or the ether. Undulations are said to be progressive when they successively traverse the different parts of a body, as the waves of the sea; and they are said to be stationary when all the particles of a body begin their vibrations simultaneously and end them at the same instant. See wave and wave-motion.
3. n. A wavy form; a form resembling that of a wave or waves; waviness.
4. n. In pathology, a particular uneasy sensation of an undulatory motion in the heart.
5. n. In surgery, a certain motion of the matter of an abscess when pressed, which indicates its fitness for opening.
6. n. A set of waved lines; a surface so marked, or such an appearance; vermiculation; waviness.
7. n. In geometry, the coming of a plane curve into a higher contact than usual with its tangent without contrary flexure.

Wiktionary

1. n. an instance or act of undulating
2. n. a wavy appearance or outline; waviness
3. n. music a tremulous tone produced by a peculiar pressure of the finger on a string
4. n. a wavelike curve; a smooth and regular rise and fall
5. n. a wavelike motion of the air; electromagnetic radiation

GNU Webster's 1913

1. n. The act of undulating; a waving motion or vibration.
2. n. A wavy appearance or outline; waviness.
3. n. The tremulous tone produced by a peculiar pressure of the finger on a string, as of a violin.
4. n. The pulsation caused by the vibrating together of two tones not quite in unison; -- called also beat.
5. n. (Physics) A motion to and fro, up and down, or from side to side, in any fluid or elastic medium, propagated continuously among its particles, but with no translation of the particles themselves in the direction of the propagation of the wave; a wave motion; a vibration.

WordNet 3.0

1. n. (physics) a movement up and down or back and forth
2. n. wavelike motion; a gentle rising and falling in the manner of waves
3. n. an undulating curve