cir·cle noun \ˈsər-kəl\
a : a closed plane curve every point of which is equidistant from a fixed point within the curve b : the plane surface bounded by such a curve
: something (as an anatomical part) in the form of a circle or section of a circle <an arterial circle>—see circle of willis
Seen & Heard
What made you want to look up circle? Please tell us where you read or heard it (including the quote, if possible).