Can you give an adjective for the word undulate?

Here are some adjectives that could describe something that undulates:

General:

* Wavy

* Curving

* Sinuous

* Rolling

* Fluctuating

* Rhythmic

* Gradual

* Swaying

* Flowing

More specific:

* Serpentine (snake-like)

* Billowing (large, swelling waves)

* Ripple-like (small, gentle waves)

* Undulating (this is a bit redundant, but it works!)

The best adjective to use will depend on the context. For example, "wavy" might be a good choice to describe hair, while "serpentine" might be more suitable for a winding road.