The flags outside the convention center undulated gently in the breeze as guests arrived.

賓客抵達時，會展中心外的旗幟在微風中輕輕飄動起伏。

Passengers watched the hills undulate below as the train approached the coastal station.

火車駛近海岸車站時，乘客看著下方的山丘連綿起伏。

The cargo ship's deck undulated with the swells, so the crew secured every container twice.

貨輪甲板隨著海浪起伏，所以船員把每個貨櫃都固定了兩次。