Wiktionary
muscle-up
n. An exercise done for strengthening the arms and upper body, in which one lifts one's own weight while hanging from a bar to a position above the bar.
Wikipedia
Muscle-up
The muscle-up (also known as a muscleup) is an advanced strength training exercise, within the domain of calisthenics. It is a combination routine of a pull-up followed by a dip. Variations exist for the rings as well as the bar.