Undulant describes things that rise and fall in waves, or things that have a wavy form, outline, or surface.

// The exhibit featured a painting with beautiful green strokes that resembled undulant hills.

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“Though tightly bound by our love of books, we bibliophiles are a sundry lot, managing our obsession in a grand variety of ways. We organize by title, by author, by genre, by topic. By color, by height, by width, by depth. … We stack books into attractive still lifes accompanied by a single tulip in a bud vase, or into risky, undulant towers poised to flatten a passing housecat.” — Monica Wood, LitHub.com, 7 May 2024

If you’re looking for an adjective that encapsulates the rising and falling of the briny sea, wave hello to undulant. While not an especially common descriptor, it is useful not only for describing the ocean itself, but for everything from rolling hills to a snake’s sinuous movement to a fever that waxes and wanes. The root of undulant is, perhaps unsurprisingly, unda, a Latin word meaning “wave.” Other English words swimming the wake of unda include inundate, “to cover with a flood,” and undulate, “to form or move in waves.”