undulation

In this case the undulation strikes but a moderate blow; the wave is not greatly broken.

From the camp of the previous evening it had evidently been hidden from view by an undulation in the surface.

Herein lies the idea of the barcarolle, the ebb and flow, the undulation of each measure.

Thirty-six hours were occupied in the journey of the great undulation from Krakatoa to its antipodes.

There was no appearance of undulation; when the lumps sank, other lumps did not rise in the intervals between them.