Serious triathletes have a host of words to describe the way their legs are feeling. On the positive side, this includes fresh, snappy, springy, zippy and many more. The converse terms are dead legs, or legs that feel heavy, gunky, shot. These terms are a way to qualify the state of our fitness and recovery. When you are under-recovered, you have dead legs. When you are fit and rested at the same time, you have springy legs.
Read more, including my advice on how to revive dead legs: http://www.ironman.com/triathlon/news/articles/2014/12/recovery-series-dead-legs.aspx#ixzz3LbRXsDxg