circle

Concise Oxford English Dictionary © 2008 Oxford University Press:
circle/ˈsɜːkl/

▶noun

• 1 a round plane figure whose boundary consists of points equidistant from the centre.

  ■ a group of people or things forming a circle.

• 2 a curved upper tier of seats in a theatre.

• 3 a group of people with a shared profession, interests, or acquaintances.

▶verb move or be situated all the way around.

■ draw a line around.

– phrases
circle the wagons N. Amer. informal unite in defence of something. [with ref. to the defensive position of a wagon train under attack.]
come (or turn) full circle return to a past position or situation.
go (or run) round in circles informal do something for a long time without achieving anything.

– origin OE, from OFr. cercle, from L. circulus ‘small ring’, dimin. of circus ‘ring’.