Something proposed to be solved by guessing or conjecture; a puzzling question; an ambiguous proposition; an enigma; hence, anything ambiguous or puzzling. [1913 Webster]
"To wring from me, and tell to them, my secret,
That solved the riddle which I had proposed." [1913 Webster]
"'T was a strange riddle of a lady." [1913 Webster]

   To explain; to solve; to unriddle. [1913 Webster]
"Riddle me this, and guess him if you can." [1913 Webster]

   To speak ambiguously or enigmatically. Shak. [1913 Webster]

riddle, n. & v.
--n.
1 a question or statement testing ingenuity in divining its answer or meaning.
2 a puzzling fact or thing or person.
--v.
1 intr. speak in or propound riddles.
2 tr. solve or explain (a riddle).

Derivative:
riddler n.

riddle, v. & n.
--v.tr. (usu. foll. by with)
1 make many holes in, esp. with gunshot.
2 (in passive) fill; spread through; permeate (was riddled with errors).
3 pass through a riddle.
--n. a coarse sieve.

Etymology:
OE hriddel, earlier hrider: cf. hridrian sift

N  cleanness, cleanliness, purity, cleaning, purification, defecation, purgation, lustration, detersion, abstersion, epuration, mundation, ablution, lavation, colature, disinfection, drainage, sewerage, lavatory, laundry, washhouse, washerwoman, laundress, dhobi, laundryman, washerman, scavenger, dustman, sweep, white wings brush, broom, besom, mop, rake, shovel, sieve, riddle, screen, filter, blotter, napkin, cloth, maukin, malkin, handkerchief, towel, sudary, doyley, doily, duster, sponge, mop, swab, cover, drugget, wash, lotion, detergent, cathartic, purgative, purifier, disinfectant, aperient, benzene, benzine benzol, benolin, bleaching powder, chloride of lime, dentifrice, deobstruent, laxative, clean, cleanly, pure, immaculate, spotless, stainless, taintless, trig, without a stain, unstained, unspotted, unsoiled, unsullied, untainted, uninfected, sweet, sweet as a nut, neat, spruce, tidy, trim, gimp, clean as a new penny, like a cat in pattens, cleaned, kempt, abstergent, cathartic, cleansing, purifying, neatly, clean as a whistle.

N  arrangement, plan, preparation, disposal, disposition, collocation, allocation, distribution, sorting, assortment, allotment, apportionment, taxis, taxonomy, syntaxis, graduation, organization, grouping, tabulation, analysis, classification, clustering, division, digestion, digest, synopsis, syntagma, table, atlas, file, database, register, organism, architecture, sieve, riddle, screen, sorter, arranged, embattled, in battle array, cut and dried, methodical, orderly, regular, systematic, In vast cumbrous array.

VB  reduce to order, bring into order, introduce order into, rally, arrange, dispose, place, form, put in order, set in order, place in order, set out, collocate, pack, marshal, range, size, rank, group, parcel out, allot, distribute, deal, cast the parts, assign the parts, dispose of, assign places to, assort, sort, sift, riddle, put to rights, set to rights, put into shape, put in trim, put in array, apportion, class, classify, divide, file, string together, thread, register, catalogue, tabulate, index, graduate, digest, grade, methodize, regulate, systematize, coordinate, organize, settle, fix, unravel, disentangle, ravel, card, disembroil, feaze.

N  opening, hole, foramen, puncture, perforation, fontanel, transforation, pinhole, keyhole, loophole, porthole, peephole, mousehole, pigeonhole, eye of a needle, eyelet, slot, opening, aperture, apertness, hiation, yawning, oscitancy, dehiscence, patefaction, pandiculation, chasm, embrasure, window, casement, abatjour, light, sky light, fan light, lattice, bay window, bow window, oriel, dormer, lantern, outlet, inlet, vent, vomitory, embouchure, orifice, mouth, sucker, muzzle, throat, gullet, weasand, wizen, nozzle, placket, portal, porch, gate, ostiary, postern, wicket, trapdoor, hatch, door, arcade, cellarway, driveway, gateway, doorway, hatchway, gangway, lich gate, way, path, thoroughfare, channel, passage, passageway, tube, pipe, water pipe, air pipe, vessel, tubule, canal, gut, fistula, adjutage, ajutage, ostium, smokestack, chimney, flue, tap, funnel, gully, tunnel, main, mine, pit, adit, shaft, gallery, alley, aisle, glade, vista, bore, caliber, pore, blind orifice, fulgurite, thundertube, porousness, porosity, sieve, cullender, colander, cribble, riddle, screen, honeycomb, apertion, perforation, piercing, terebration, empalement, pertusion, puncture, acupuncture, penetration, key, opener, master key, password, combination, passe- partout, open, perforated, perforate, wide open, ajar, unclosed, unstopped, oscitant, gaping, yawning, patent, tubular, cannular, fistulous, pervious, permeable, foraminous, vesicular, vasicular, porous, follicular, cribriform, honeycombed, infundibular, riddled, tubulous, tubulated, piped, tubate, opening, aperient, Int, open sesame!.

VB  open, ope, gape, yawn, bilge, fly open, perforate, pierce, empierce, tap, bore, drill, mine, tunnel, transpierce, transfix, enfilade, impale, spike, spear, gore, spit, stab, pink, puncture, lance, stick, prick, riddle, punch, stave in, cut a passage through, make way for, make room for, uncover, unclose, unrip, lay open, cut open, rip open, throw open, pop open, blow open, pry open, tear open, pull open.

N  unintelligibility, incomprehensibility, imperspicuity, inconceivableness, vagueness, obscurity, ambiguity, doubtful meaning, uncertainty, perplexity, spinosity, obscurum per obscurius, mystification, latency, transcendentalism, paradox, oxymoron, riddle, enigma, puzzle, diagnus vindice nodus, sealed book, steganography, freemasonry, pons asinorum, asses' bridge, high Dutch, Greek, Hebrew, jargon, unintelligible, unaccountable, undecipherable, undiscoverable, unknowable, unfathomable, incognizable, inexplicable, inscrutable, inapprehensible, incomprehensible, insolvable, insoluble, impenetrable, illegible, as Greek to one, unexplained, paradoxical, enigmatic, enigmatical, puzzling (secret), indecipherable, obscure, dark, muddy, clear as mud, seen through a mist, dim, nebulous, shrouded in mystery, opaque, dense, undiscernible, misty, hidden, latent, indefinite, garbled, perplexed, undetermined, vague, loose, ambiguous, mysterious, mystic, mystical, acroamatic, acroamatical, metempirical, transcendental, occult, recondite, abstruse, crabbed, inconceivable, inconceptible, searchless, above comprehension, beyond comprehension, past comprehension, beyond one's depth, unconceived, inexpressible, undefinable, incommunicable, unpredictable, unforeseeable, it's Greek to me.

N  secret, dead secret, profound secret, arcanum, mystery, latency, Asian mystery, sealed book, secrets of the prison house, le desous des cartes, enigma, riddle, puzzle, nut to crack, conundrum, charade, rebus, logogriph, monogram, anagram, Sphinx, crux criticorum, maze, labyrinth, Hyrcynian wood, intricacy, meander, problem, paradox, unintelligibility, terra incognita, secret, involved, labyrinthine, labyrinthian, mazy, confidential, top secret.

james riddle hoffa, riddle canon