1. To breathe hard after exertion or to be unable to catch your breath after an activity.
2. To lose any chance of winning after a certain point.
1. While mountain biking for example: Man, I'm suckin wind after climbing that hill.
2. A: How do you think you'll do in that 5 mile race? B: Crappy - after 3 miles, I'm useless, I just suck wind.