Housing prices are galloping upward, making it unaffordable for many people.

galloping 是动词 gallop 的现在分词形式。gallop 原指马"飞奔、疾驰"，这里用作比喻，形容房价像马奔跑一样"飞速上涨"。这种用法生动形象地表现了房价上涨的速度之快。