The Collaborative International Dictionary of English v.0.48:

chin-up \chin-up\ n.
   an arm exercise performed by pulling oneself up on a
   horizontal bar until the chin is level with or above the bar.
   [WordNet 1.5] chin-wag

WordNet (r) 3.0 (2006):

chin-up
    n 1: an arm exercise performed by pulling yourself up on a
         horizontal bar until your chin is level with the bar [syn:
         pull-up, chin-up]