1.  A circular letter, or paper, usually printed, copies of which are addressed or given to various persons; as, a business circular. [1913 Webster]

2.  A sleeveless cloak, cut in circular form. [1913 Webster]

circular, adj. & n.
--adj.
1 a having the form of a circle. b moving or taking place along a circle (circular tour).
2 Logic (of reasoning) depending on a vicious circle.
3 (of a letter or advertisement etc.) printed for distribution to a large number of people.
--n. a circular letter, leaflet, etc.

Idiom:
circular saw a power saw with a rapidly rotating toothed disc.

Derivative:
circularity n. circularly adv.

Etymology:
ME f. AF circuler, OF circulier, cerclier f. LL circularis f. L circulus CIRCLE

N  correspondence, letter, epistle, note, billet, post card, missive, circular, favor, billet-doux, chit, chitty, letter card, picture post card, postal, card, despatch, dispatch, bulletin, these presents, rescript, rescription, post, epistolary, furor scribendi.

N  booklet, writing, work, volume, tome, opuscule, tract, tractate, livret, brochure, libretto, handbook, codex, manual, pamphlet, enchiridion, circular, publication, chap book, part, issue, number livraison, album, portfolio, periodical, serial, magazine, ephemeris, annual, journal, paper, bill, sheet, broadsheet, leaf, leaflet, fly leaf, page, quire, ream, chapter, section, head, article, paragraph, passage, clause, endpapers, frontispiece, cover, binding, folio, quarto, octavo, duodecimo, sextodecimo, octodecimo, encyclopedia, encompilation, library, bibliotheca, press, definitive work, treatise, comprehensive treatise (dissertation), writer, author, litterateur, essayist, journalism, pen, scribbler, the scribbling race, literary hack, Grub-street writer, writer for the press, gentleman of the press, representative of the press, adjective jerker, diaskeaust, ghost, hack writer, ink slinger, publicist, reporter, penny a liner, editor, subeditor, playwright, poet, bookseller, publisher, bibliopole, bibliopolist, librarian, bookstore, bookshop, bookseller's shop, knowledge of books, bibliography, book learning, among the giant fossils of my past, craignez tout d'un auteur en courroux, for authors nobler palms remain, I lived to write and wrote to live, look in thy heart and write, there is no Past so long as Books shall live, the public mind is the creation of the Master-Writ, volumes that I prize above my dukedom.

N  curvature, curvity, curvation, incurvature, incurvity, incurvation, bend, flexure, flexion, flection, conflexure, crook, hook, bought, bending, deflection, deflexion, inflection, inflexion, concameration, arcuation, devexity, turn, deviation, detour, sweep, curl, curling, bough, recurvity, recurvation, sinuosity, kink, carve, arc, arch, arcade, vault, bow, crescent, half-moon, lunule, horseshoe, loop, crane neck, parabola, hyperbola, helix, spiral, catenary, festoon, conchoid, cardioid, caustic, tracery, arched ceiling, arched roof, bay window, bow window, sine curve, spline, spline curve, spline function, obliquity, curved, curviform, curvilineal, curvilinear, devex, devious, recurved, recurvous, crump, bowed, vaulted, hooked, falciform, falcated, semicircular, crescentic, sinusoid, parabolic, paraboloid, luniform, lunular, semilunar, conchoidal, helical, double helical, spiral, kinky, cordiform, cordated, cardioid, heart shaped, bell shaped, boat shaped, crescent shaped, lens shaped, moon shaped, oar shaped, shield shaped, sickle shaped, tongue shaped, pear shaped, fig shaped, kidney-shaped, reniform, lentiform, lenticular, bow-legged, oblique, circular, aduncated, arclike, arcuate, arched, beaked, bicorn, bicornuous, bicornute, clypeate, clypeiform, cymbiform, embowed, galeiform, hamate, hamiform, hamous, hooked, linguiform, lingulate, lobiform, lunate, navicular, peltate, remiform, rhamphoid, rostrate, rostriferous, rostroid, scutate, scaphoid, uncate, unguiculate, unguiform.

N  circularity, roundness, rotundity, circle, circlet, ring, areola, hoop, roundlet, annulus, annulet, bracelet, armlet, ringlet, eye, loop, wheel, cycle, orb, orbit, rundle, zone, belt, cordon, band, contrate wheel, crown wheel, hub, nave, sash, girdle, cestus, cincture, baldric, fillet, fascia, wreath, garland, crown, corona, coronet, chaplet, snood, necklace, collar, noose, lasso, lassoo, ellipse, oval, ovule, ellipsoid, cycloid, epicycloid, epicycle, semicircle, quadrant, sextant, sector, sphere, round, rounded, circular, annular, orbicular, oval, ovate, elliptic, elliptical, egg-shaped, pear-shaped, cycloidal, spherical, I watched the little circles die.

N  publication, public announcement, promulgation, propagation, proclamation, pronunziamento, circulation, indiction, edition, hue and cry, publicity, notoriety, currency, flagrancy, cry, bruit, hype, vox populi, report, the Press, public press, newspaper, journal, gazette, daily, telegraphy, publisher, imprint, circular, circular letter, manifesto, advertisement, ad, placard, bill, affiche, broadside, poster, notice, published, current, in circulation, public, notorious, flagrant, arrant, open, trumpet-tongued, encyclical, encyclic, promulgatory, exoteric, publicly, in open court, with open doors, Int, Oyez!, O yes!, notice!, notice is hereby given, this is to give, these are to give notice, nomina stultorum parietibus haerent, semel emissum volat irrevocabile verbum.