char ‧ ley horse /ˌtʃɑːli ˈhɔːs $ ˌtʃɑːrli ˈhɔːrs/ BrE AmE noun [countable, singular] American English informal
[ Date: 1800-1900 ; Origin: Charley male name, from Charles ]
a pain in a large muscle, for example in your leg, caused by the muscle becoming tight SYN cramp