center

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

• noun A point or place that is equally distant from the sides or outer boundaries of something; the middle.
• noun A point equidistant from the vertices of a regular polygon.
• noun A point equidistant from all points on the circumference of a circle or on the surface of a sphere.
• noun A point around which something rotates or revolves.
• noun A part of an object that is surrounded by the rest; a core.
• noun A place where a particular activity or service is concentrated.
• noun A point of origin, as of influence, ideas, or actions.
• noun An area of dense population.
• noun A person or thing that is the chief object of attention, interest, activity, or emotion.
• noun A person, object, or group occupying a middle position.
• noun A political group or a set of policies representing a moderate view between those of the right and the left.
• noun Physiology A group of neurons in the central nervous system that control a particular function.
• noun Sports A player who holds a middle position on the field, court, or forward line in some team sports, such as hockey and basketball.
• noun Football An offensive lineman who snaps the ball to begin a play, usually positioned in the middle of the line.
• noun Baseball Center field.
• noun A small conical hole made in a piece of work with a center punch so that a drill can be accurately positioned within it.
• noun A bar with a conical point used to support work, as during turning on a lathe.
• noun Architecture A centering.
• intransitive verb To place in or at the center.
• intransitive verb To direct toward a center or central point; concentrate or focus.
• intransitive verb To pass (a ball or puck) toward the center of a playing area.
• intransitive verb To play as a center on (a line), as in ice hockey.
• intransitive verb Football To hike (the ball) to begin a down.
• intransitive verb To be concentrated; cluster.
• intransitive verb To have a central theme or concern; be focused.
• intransitive verb Sports To play as a center.

from The Century Dictionary.

• noun An arched frame on which the arch of a bridge or any vaulted work is supported during its construction: same as centering.
• noun A point so situated with regard to a locus that all chords of the locus, drawn through the point, are bisected in it. The pole of a straight at infinity with respect to a certain conic is the center of the conic.
• noun In foot-ball, roller-polo, basket-ball, hockey, and other games, the one who plays in the middle of the forward line; in foot-ball, the snap-back.
• noun Any group or collection of cells, within the brain, that subserves a single function.
• noun The point at which a body must be supported in order to remain quietly balanced when the wind is blowing on it. For plane plates the location of the center as determined by Kümmer varies with the dimensions of the plate, but is always in front of the center of the figure.
• noun The visual center of the retina, where sight is keenest. Also called the yellow spot. See macula lutea, under macula and also under retina (10).
• noun The center about which any moving piece or assemblage of pieces in a mechanism can be supposed to be rotating at any instant. Notwithstanding that the relative positions of such pieces or links may be constantly changing, yet at any instant they will be turning round a common center, which, however, shifts in space with each new relative position of the links. The determination of the virtual center, as it is sometimes called, is of use in estimating the relative velocity-ratios and forces acting on the bodies.
• To place on a center; fix on a central point.
• To collect to a point.
• To be placed in a center or in the middle.
• To meet or be collected in one point; be concentrated or united in or about a focus, literally or figuratively.
• noun That point from which all the points of a circumference or of the superficies of a sphere are equally distant: in a regular figure or body the center is a point so situated with reference to the circumscribed circle or sphere.
• noun The middle point or part of any surface or solid.
• noun The fixed point once supposed to exist in the middle of the universe.
• noun In heraldry, the middle point, whether of the whole field or of the chief or base.
• noun One of the points of the two lathe-spindles on which an object to be turned is placed, distinguished as the front or live center, on the spindle of the head-stock, and the dead center, on that of the tail-stock: also, one of two similar points for holding an object to be operated on by some other machine, as a planing-machine, and enabling the object to be turned round on its axis.
• noun A point of concentration or diffusion; the nucleus about which or into which things are collected or from which they diverge or emerge: as, a center of attraction; a center of power.
• noun The central object; the principal point; the point of chief interest: as, the center of a diplomatic negotiation.
• noun 8. Milit.: