From WordNet (r) 3.0 (2006):
undulate adj 1: having a wavy margin and rippled surface v 1: stir up (water) so as to form ripples [syn: ripple, ruffle, riffle, cockle, undulate] 2: occur in soft rounded shapes; "The hills rolled past" [syn: roll, undulate] 3: move in a wavy pattern or with a rising and falling motion; "The curtains undulated"; "the waves rolled towards the beach" [syn: roll, undulate, flap, wave] 4: increase and decrease in volume or pitch, as if in waves; "The singer's voice undulated"