According to The Free Dictionary's medical dictionary, a uniaxial joint is one that allows for motion around one particular axis. Any point of union between bones is a joint.
Uniaxial joints contrast with biaxial joints that allow for motion around two main axes. In a biaxial joint, the main axes around which motion is possible are at right angles to one another. The Free Dictionary lists numerous other types of joints, including synovial joints that enable free motion due to the presence of an articular capsule containing synovial membrane that surrounds the point at which the bones meet one another.