undulate
     adj : having a sinuate margin and rippled surface
     v 1: stir up (water) so as to form ripples [syn: {ripple}, {ruffle},
           {riffle}, {cockle}]
     2: occur in soft rounded shapes; "The hills rolled past" [syn:
        {roll}]
     3: move in a wavy pattern or with a rising and falling motion;
        "The curtains undulated"; "the waves rolled towards the
        beach" [syn: {roll}, {flap}, {wave}]
     4: increase and decrease in volume or pitch, as if in waves;
        "The singer's voice undulated"
Source: WordNet® 2.0