Noun

1. : A two-dimensional geometric figure, a line, consisting of the set of all those points in a plane that are equally distant from another point.

   The set of all points (x, y) such that $(x-1)^2\; +\; y^2\; =\; r^2$ is a circle of radius r around the point (1, 0).

2. A two-dimensional geometric figure, a disk, consisting of the set of all those points of a plane at a distance less than or equal to a fixed distance from another point.
3. Any thin three-dimensional equivalent of the geometric figures.

   Put on your dunce-cap and sit down on that circle.

4. A curve that more or less forms part or all of a circle.

   move in a circle

5. Orbit.
6. A specific group of persons.

   inner circle

   circle of friends

7. A line comprising two semicircles of 30 yards radius centred on the wickets joined by straight lines parallel to the pitch used to enforce field restrictions in a one-day match.

• (two-dimensional outline geometric figure): coil (not in mathematical use), ring (not in mathematical use), loop (not in mathematical use)
• (two-dimensional solid geometric figure): disc/disk (in mathematical and general use), round (not in mathematical use; UK & Commonwealth only)
• (curve): arc, curve
• (orbit): orbit

1. To travel around along a curved path.
2. To surround.
3. To place or mark a circle around.

   Circle the jobs that you are interested in applying for.

4. To travel in circles.

   Vultures circled overhead.