Merriam-Webster Collegiate Dictionary - circular

 I. adjective  Etymology: Middle English circuler, from Middle French, from Late Latin ~is, from Latin circulus circle  Date: 15th century  1.  a. having the form of a circle ; round a ~ orbit  b. moving in or describing a circle or spiral a ~ staircase  2.  a. of or relating to a circle or its mathematical properties a ~ arc  b. having a ~ base or bases a ~ cylinder  3. circuitous, indirect  4. marked by or moving in a cycle  5. being or involving reasoning that uses in the argument or proof a conclusion to be proved or one of its unproved consequences  6. intended for circulation a ~ letter  • ~ity noun  • ~ly adverb  • ~ness noun  II. noun  Date: 1789 a paper (as a leaflet) intended for wide distribution