noun. Any of several types of bone articulation permitting free motion in a joint, as that of the shoulder or hip.

noun. In anatomy, that articulation of bones which leaves them free to move in some or any direction; free, as distinguished from fixed, arthrosis; thorough-joint: applied both to the joints themselves and to the motion resulting from such mechanism.

noun. A form of articulation which admits of considerable motion; a complete joint; abarticulation. See articulation.

noun. A joint that can move freely in various planes

noun. a joint so articulated as to move freely

"In a considerable part of their extent, especially in advanced life, they are separated by a space containing a synovia-like fluid, and hence the joint presents the characteristics of a diarthrosis."

rotatory diarthrosis  

abarticulation  synovial joint  

articulation  diarthroses