undulating

Concise Oxford English Dictionary © 2008 Oxford University Press:
undulate

▶verb /ˈʌndjʊleɪt/ move with a smooth wave-like motion.

■ (usu. as adj. undulating) have a wavy form or outline.

▶adjective /ˈʌndjʊlət/ Botany & Zoology having a wavy surface or edge.

– derivatives
undulately adverb,
undulation noun,
undulatory adjective.

– origin C17: from late L. undulatus, from L. unda ‘a wave’.