老人在公园里悠闲地散步，欣赏着周围的花草。

The old man was perambulating in the park, enjoying the flowers and plants around him.

perambulating 是动词 perambulate 的现在分词形式。perambulate 由前缀 per-（表示"穿过、遍及"）和 ambul（来自拉丁语 ambulare，意为"行走"）组成，字面意思是"四处走动"，通常指"悠闲地散步"或"漫步"。