hinge joint

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A joint, such as the elbow, in which a convex part of one bone fits into a concave part of another, allowing motion in only one plane.

GNU Webster's 1913

1. n. (Anat.), (Mech.) Any joint resembling a hinge, by which two pieces are connected so as to permit relative turning in one plane.

WordNet 3.0

1. n. a freely moving joint in which the bones are so articulated as to allow extensive movement in one plane
2. n. a joint allowing movement in one plane only