fulcrum

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. The point or support on which a lever pivots.
2. n. Zoology An anatomical structure that acts as a hinge or a point of support.
3. n. An agent through which vital powers are exercised.

Century Dictionary and Cyclopedia

1. n. A prop or support.
2. n. In mech., the point of rest about which a lever turns in lifting a body; also, a prop or support for a lever at this point. See lever.
3. n. In botany, an accessory organ, such as a bract, stipule, spine, etc., or one of the aërial roots of climbing plants, as of ivy.
4. n. In mycology, one of the radiating appendages of the perithecia of Erysipheæ.
5. n. In entomology, the inferior horny surface of the ligula, found in many Hymenoptera, etc. Also called the os hyoideum.
6. n. In ichthyology, a special scale or spine on the fore edge of the anterior fin-rays of the dorsal or caudal fins of certain ganoid fishes, as Lepidosteus, Acipenser, and many fossil genera.
7. To furnish with a fulcrum; establish as a fulcrum.
8. n. In rotifers, the short stem of the incus, one of the parts of the mastax or pharyngeal mill.
9. n. In the trilobites, the bend or the point of abrupt curvature of the thoracic pleura, which divides them into proximal and distal portions.

Wiktionary

1. n. mechanics The support about which a lever pivots.

GNU Webster's 1913

1. n. A prop or support.
2. n. (Mech.) That by which a lever is sustained, or about which it turns in lifting or moving a body.
3. n. (Bot.), rare An accessory organ such as a tendril, stipule, spine, and the like.
4. n. The horny inferior surface of the lingua of certain insects.
5. n. One of the small, spiniform scales found on the front edge of the dorsal and caudal fins of many ganoid fishes.
6. n. (Anat.) The connective tissue supporting the framework of the retina of the eye.

WordNet 3.0

1. n. the pivot about which a lever turns