undulation
un.du.la.tion \.*n-j*-'la--sh*n, .*n-d(y)*-\ n 1a: a rising and falling in waves 1b: a wavelike motion to and fro in a fluid or elastic medium propagated co ntinuously among its particles but with little or no permanent translation of the particles in the direction of the propagation : VIBRATION 2: the pulsation caused by the vibrating together of two tones not quite in unison 3: a wavy appearance, outline, or form : WAVINESS