un·du·la·tion [ʌndjuˈleɪʃn] n. 1. A regular rising and falling or movement to alternating sides; movement in waves. 2. A wavelike form, outline, or appearance.
Etymology: 1640s, from Medieval Latin *undulatio, from Late Latin undulatus "wavy, undulated," from undula "wavelet," diminutive of Latin unda "wave" (see water).
I really wanted to do undulate, because verbs are just cooler than nouns, but the etymology for undulate was: see undulation. Boring.