Ball-and-socket joint, also called spheroidal joint, in vertebrate anatomy, a joint in which the rounded surface of a bone moves within a depression on another bone, allowing greater freedom of movement than any other kind of joint. The ball and socket joint (or spheroid joint) is a type of synovial joint in which the ball-shaped surface of one rounded bone fits into the cup-like depression of. Ball-and-socket joint definition is - a joint in which a ball moves within a socket so as to allow rotary motion in every direction within certain limits. Ball-and-socket joint: A joint in which the round end of a bone fits into the cavity of another bone. Ball-and-socket joint definition, a joint in which the rounded end of one bone fits into a cuplike end of the other bone, allowing for relatively free rotary motion,. Answer · The ball and socket joint is a type of synovial joint in which the ball- shaped surface of one rounded bone fits into the cup-like depression.