circular

(noun) an advertisement (usually printed on a page or in a leaflet) intended for wide distribution. Synonyms: handbill, bill, broadside, broadsheet, flier, flyer, throwaway. Example: "He mailed the circular to all subscribers."

(adj) having a circular shape. Synonyms: round (vs. square).

(adj) describing a circle; moving in a circle. Synonyms: rotary, orbitual. Example: "The circular motion of the wheel."