Undulate is a formal word that means “to move or be shaped like waves.”

// On the approach to the tulip festival, visitors are greeted by a large field of the colorful flowers undulating in the wind.

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“When sufficiently heated, the fresh cheese contracts, sweating whey from the curds that provides liquid to cook the dough, which will plump up and undulate slightly as it expands.” — Karima Moyer-Nocchi, The Epic History of Macaroni and Cheese: From Ancient Rome to Modern America, 2026

Undulate and inundate (“to cover something with a flood of water”) are word cousins that flow from unda, the Latin word for “wave.” No surprise there. But would you have guessed that abound, surround, and redound are also unda offspring? While their modern definitions have nothing to do with waves or water, at some point in their early histories, they all meant “to overflow,” and caught a wave from there.