What does undulate mean?

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From our dictionary:

un•du•late

Pronunciation: (
v.un'ju-lAt", un'dyu-, -du-;
adj.un'ju-lit, -lAt", un'dyu-, -du-),
[key]
v., -lat•ed, -lat•ing,
adj.


v.i.
1. to move with a sinuous or wavelike motion; display a smooth rising-and-falling or side-to-side alternation of movement: The flag undulates in the breeze.
2. to have a wavy form or surface; bend with successive curves in alternate directions.
3. (of a sound) to rise and fall in pitch: the wail of a siren undulating in the distance.

v.t.
1. to cause to move in waves.
2. to give a wavy form to.

adj.
Also,un'du•lat"ed.having a wavelike or rippled form, surface, edge, etc.; wavy.