walker-on

例句：

1. 1. The elderly man was a walker-on for the marathon.
   这位老人是马拉松的步行者。
2. 2. The children were walking on the grass in the park.
   孩子们在公园里走在草地上。
3. 3. He is a walker-on for the local newspaper.
   他是当地报纸的步行记者。