undulate -
increase and decrease in volume or pitch, as if in waves; "The singer's voice undulated"
change undergo a change; become different in essence; losing one's or its original nature; "She changed completely as she grew older"; "The weather changed last night"
undulate -
move in a wavy pattern or with a rising and falling motion; "The curtains undulated"; "the waves rolled towards the beach"
fold up,
fold,
turn up incorporate a food ingredient into a mixture by repeatedly turning it over without stirring or beating; "Fold the egg whites into the batter"
undulate -
occur in soft rounded shapes; "The hills rolled past"
