adjective
Etymology: from present participle of undulate
1. : rising and falling in waves : fluctuating
I often gaze on that waste of undulating water — L.P.Smith
2. : resembling waves in form : having a wavy outline : rolling , scalloped
broad, undulating prairie land — American Guide Series: Minnesota
her small white straw hat had an undulating brim — Sydney (Australia) Bulletin
3. : rising and falling in volume, pitch, or metrical stress or quantity
undulating string arpeggios — Julian Herbage