knee

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The joint between the thigh and the lower leg, formed by the articulation of the femur and the tibia and covered anteriorly by the patella.
• noun The region of the leg that encloses and supports this joint.
• noun An analogous joint or part of a leg of a quadruped vertebrate.
• noun The joint between the femur and the tibia in an insect leg.
• noun Something resembling the human knee, such as a bent piece of pipe.
• noun The part of a garment, as of trousers, that covers the knee.
• noun A vertical, often conical, woody projection arising from the roots of certain swamp-growing trees.
• transitive verb To strike with the knee.
• idiom (take a knee) To kneel down on one knee.
• idiom Football (take a knee) To kneel down on one knee while holding the ball so as to down the ball, as in one's own end zone for a touchback.

from The Century Dictionary.

• To go down on the knees; kneel.
• To kneel to.
• To pass over on the knees.
• In ship-building, to fit with a knee or knees.
• noun In graphics, a break or abrupt change in a plotted curve.
• noun A natural prominence; a rock, hill, or part of a hill.
• noun The joint between the two principal parts of the leg of man or the hind limb of lower animals; the articulation of the thigh-bone or femur with the tibia or fibula, or with both. See def. 2 and knee-joint.
• noun Some other joint in animals other than man, likened to the human knee-joint or regarded as its representative
• noun The tarsal articulation or heel-joint of a bird; the suffrago: as, tibiæ feathered down to the knee, The joint of an insect's leg connecting the femur and the tibia. In descriptions the word is often used to indicate the apex of the femur, sometimes including the base of the tibia: as, black or yellow knees.
• noun Something resembling the knee in shape.
• noun Specifically— In ship-building, a piece of timber or iron having an angular bend like that of the knee, used to secure the beams of a ship to her sides or timbers. The branches of the knee form an angle of greater or smaller extent, according to the situation of the pieces which it is designed to unite. Lodging-knees are knees fixed parallel to the deck. Hanging-knees are knees placed vertically, generally under a deck-beam. Diagonal hanging-knees are knees which cross the timbers in a slanting direction. Also knee-piece. See cut nnder stern.
• noun In carpentry, a piece of wood having a natural bend, or sawn into shape, and fitted into an angle.
• noun In architecture, a part of the back of a hand-rail of a convex form: the reverse of a ramp, which is concave.
• noun In botany a spur-like process on the roots of the bald cypress, Taxodium distichum, by which a part of their surface is kept above water.
• noun A genuflection; reverence.

from the GNU version of the Collaborative International Dictionary of English.

• transitive verb obsolete To supplicate by kneeling.
• noun In man, the joint in the middle part of the leg.
• noun The joint, or region of the joint, between the thigh and leg.
• noun In the horse and allied animals, the carpal joint, corresponding to the wrist in man.
• noun (Mech. & Shipbuilding) A piece of timber or metal formed with an angle somewhat in the shape of the human knee when bent.
• noun A bending of the knee, as in respect or courtesy.
• noun See under Breeches.
• noun (Bot.) butcher's broom.
• noun See in the Vocabulary.
• noun timber with knees or angles in it.
• noun [Obs.] tribute paid by kneeling; worship by genuflection.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun In humans, the joint or the region of the joint in the middle part of the leg between the thigh and the shank.
• noun In the horse and allied animals, the carpal joint, corresponding to the wrist in humans.
• noun The part of a garment that covers the knee.
• noun shipbuilding A piece of timber or metal formed with an angle somewhat in the shape of the human knee when bent.
• noun archaic An act of kneeling, especially to show respect or courtesy.
• noun Any knee-shaped item or sharp angle in a line, "the knee of a graph", an inflection point.
• noun A blow made with the knee; a kneeing.
• verb transitive, archaic To kneel to.
• verb transitive To poke or strike with the knee.