un·du·la·tion 
(ŭn′jə-lāshən, ŭn′dyə-, -də-)
(ŭn′jə-lāshən, ŭn′dyə-, -də-)n.
1. A regular rising and falling or movement to alternating sides; movement in waves.
2. A wavelike form, outline, or appearance.
3. One of a series of waves or wavelike segments.