1. 马拉松赛跑(全程26英里，约合42公里)
A marathon is a race in which people run a distance of 26 miles, which is about 42 km.
2. 马拉松式的;漫长而累人的;耗时费力的
If you use marathon to describe an event or task, you are emphasizing that it takes a long time and is very tiring.