malleolus

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Either of the two rounded protuberances on each side of the ankle, the inner formed by a projection of the tibia and the outer by a projection of the fibula.

Century Dictionary and Cyclopedia

1. n. In anatomy, a bony protuberance on either side of the ankle. The two together contribute to the stability of the ankle-joint, by locking the astragalus so as to prevent lateral and rotatory movements. In man the outer malleolus is formed by the fibula, the inner by the tibia; and each forms a sort of pulley or trochlea around which wind the tendons of important extensor muscles of the foot. The malleoli are little distinguished in most animals, owing to the different set of the foot upon the leg, or the different configuration of the parts. When, as often occurs, the fibula does not reach the ankle, the outer malleolus is wanting unless formed by the tibia. In birds the condyles of the tibia, constituted by ankylosis of proximal tarsal bones, take the name and place of malleoli.
2. n. In botany, a layer; a shoot bent into the ground and half divided at the bend, whence it emits roots.
3. n. [capitalized] In conch., a genus of bivalve shells.

Wiktionary

1. n. The bony prominence on each side of the ankle joint.

GNU Webster's 1913

1. n. (Anat.) A projection at the distal end of each bone of the leg at the ankle joint. The malleolus of the tibia is the internal projection, that of the fibula the external.
2. n. “ A layer, ” a shoot partly buried in the ground, and there cut halfway through.