资料来源 : WordNet®

ball-and-socket joint
     n 1: a freely moving joint in which a sphere on the head of one
          bone fits into a rounded cavity in the other bone [syn:
          {spheroid joint}, {cotyloid joint}, {enarthrodial joint},
           {enarthrosis}, {articulatio spheroidea}]
     2: a joint that can rotate within a socket