circle

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

• noun A plane curve everywhere equidistant from a given fixed point, the center.
• noun A planar region bounded by a circle.
• noun Something, such as a ring, shaped like such a plane curve.
• noun A circular or nearly circular course, circuit, or orbit.
• noun A traffic circle.
• noun A series or process that finishes at its starting point or continuously repeats itself; a cycle.
• noun A group of people sharing an interest, activity, or achievement.
• noun A territorial or administrative division, especially of a province, in some European countries.
• noun A sphere of influence or interest; domain.
• noun Logic A vicious circle.
• intransitive verb To make or form a circle around.
• intransitive verb To move in a circle around.
• intransitive verb To move in a circle. synonym: turn.
• idiom (circle the wagons) To take a defensive position; become defensive.

from The Century Dictionary.

• To encircle; encompass; surround; inclose.
• To move around; revolve around.
• To make to move in a circle or to revolve.
• To move in a round or circle; circulate; revolve or turn circularly.
• To form a circle; assume or have the form of a circle.
• noun A bookbinders' wheel-shaped tool, having a design engraved on the rim or edge.
• noun A circle of communicating arterioles on the sclerotic surrounding the optic nerve.
• noun A ring of fibrocartilage which gives support to the auriculoventricular valve on each side of the heart. Also called circulus callosus Halleri.
• noun The circumcircle of the triangle of similitude of three figures directly similar.
• noun Second Lemoine circle. Same as cosine circle.
• noun In gearing, the pitch-circle.
• noun In surgery, the passage of chyme, after gastro-enterostomy, through the artificial opening into the intestine, and then its regurgitation, in consequence of antiperistaltic action, through the pylorus back into the stomach.
• noun The mutually accelerating action of two independent but coexisting diseases.
• noun In elementary geom., a plane figure whose periphery is everywhere equally distant from a point within it, the center; in modern geom., the periphery of such a figure; a circumference.
• noun A circular formation or arrangement; a circlet; a ring: as, a circle of stones or of lights.
• noun A round body; a sphere; an orb.
• noun Circuit; course.
• noun Compass; inclosure.
• noun Something conceived as analogous to a circle; specifically, a number of persons intimately related to a central interest, person, or event; hence, a number of persons associated by any tie; a coterie; a set: as, a circle of ideas; to move in the higher circles of society; the circles of fashion; the family circle.
• noun A series ending where it begins, and perpetually repeated.
• noun A complete system, involving several subordinate divisions: as, the circle of the sciences.
• noun Circumlocution; indirect form of speech.
• noun In logic, an inconclusive form of argument, in which two or more unproved statements, or their equivalents, are used to prove each other: often called a vicious circle, or argument in a circle.
• noun The English equivalent of the name given in some countries, as in Germany, to certain administrative divisions.
• noun In astronomy and geodesy, a piece of metal or glass with lines engraved upon it so as to form graduations dividing the circumference of a circle into equal parts; hence, any instrument of which such a graduated circle forms the part that is most important or most difficult to make.
• noun A small shuttle made in the form of a horseshoe, and moving in a circular path.
• noun In geography, a small circle the plane of which is perpendicular to the axis of the earth; a circle of the globe parallel to the equator: more usually called a parallel of latitude.
• noun A line showing the hour on a sun-dial.
• noun A circle of declination: referred to as the two-hour circle, etc., especially as the six-hour circle.

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

• intransitive verb To move circularly; to form a circle; to circulate.
• transitive verb To move around; to revolve around.
• transitive verb To encompass, as by a circle; to surround; to inclose; to encircle.
• transitive verb to confine; to hem in; to keep together; as, to circle bodies in.
• noun A plane figure, bounded by a single curve line called its circumference, every part of which is equally distant from a point within it, called the center.
• noun The line that bounds such a figure; a circumference; a ring.