n. & v.
n. 1 a a round plane figure whose circumference is everywhere equidistant from its centre. b the line enclosing a circle. 2 a roundish enclosure or structure. 3 a ring. 4 a curved upper tier of seats in a theatre etc. (dress circle). 5 a circular route. 6 Archaeol. a group of (usu. large embedded) stones arranged in a circle. 7 Hockey = striking-circle. 8 persons grouped round a centre of interest. 9 a set or class or restricted group (literary circles; not done in the best circles). 10 a period or cycle (the circle of the year). 11 (in full vicious circle) a an unbroken sequence of reciprocal cause and effect. b an action and reaction that intensify each other (cf. virtuous circle). c the fallacy of proving a proposition from another which depends on the first for its own proof.
v. 1 intr. (often foll. by round, about) move in a circle. 2 tr. a revolve round. b form a circle round. circle back move in a wide loop towards the starting-point. come full circle return to the starting-point. go round in circles make no progress despite effort. great (or small) circle a circle on the surface of a sphere whose plane passes (or does not pass) through the sphere's centre. run round in circles colloq. be fussily busy with little result. circler n.
[ ME f. OF cercle f. L circulus dimin. of circus ring ]