adjective

having the form of a circle.

the building features a circular atrium

round,disc-shaped,disc-like,ring-shaped,hoop-shaped,hooplike,annular,cycloidal,discoid,discoidal

noun

a letter or advertisement that is distributed to a large number of people.

I received a circular from a building society

leaflet,pamphlet,handbill,flyer,advertisement,notice,mailer,folder,dodger