Wiktionary
ham hock
n. The cut of meat at the joint between the leg and foot of a hog.
WordNet
ham hock
n. a small cut of meat from the leg just above the foot
Wikipedia
Ham hock
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A ham hock (or hough) or pork knuckle is the joint between the tibia/fibula and the metatarsals of the foot, where the foot was attached to the hog's leg. It is the portion of the leg that is neither part of the ham proper nor the foot or ankle, but rather the extreme shank end of the leg bone.