1.  ridiculous(s = adj.all) pathetic, silly - inspiring scornful pity; "how silly an ardent and unsuccessful wooer can be especially if he is getting on in years"
Derived form noun ridicule₂

2.  ridiculous(s = adj.all) absurd, cockeyed, derisory, idiotic, laughable, ludicrous, nonsensical, preposterous - incongruous;inviting ridicule; "the absurd excuse that the dog ate his homework"; "that's a cockeyed idea"; "ask a nonsensical question and get a nonsensical answer"; "a contribution so small as to be laughable"; "it is ludicrous to call a cottage a mansion"; "a preposterous attempt to turn back the pages of history"; "her conceited assumption of universal interest in her rather dull children was ridiculous"
Derived form noun ridiculousness₁

3.  ridiculous(s = adj.all) farcical, ludicrous - broadly or extravagantly humorous; resembling farce; "the wild farcical exuberance of a clown"; "ludicrous green hair"
Derived forms noun ridicule₁, noun ridiculousness₁

1.  Fitted to excite ridicule; absurd and laughable; unworthy of serious consideration; as, a ridiculous dress or behavior. [1913 Webster]
"Agricola, discerning that those little targets and unwieldy glaives ill pointed would soon become ridiculous against the thrust and close, commanded three Batavian cohorts . . . to draw up and come to handy strokes." [1913 Webster]

2.  Involving or expressing ridicule. [1913 Webster]
"[It] provokes me to ridiculous smiling." [1913 Webster]

ridiculous, adj.
1 deserving or inviting ridicule.
2 unreasonable, absurd.

Derivative:
ridiculously adv. ridiculousness n.

Etymology:
L ridiculosus (as RIDICULE)

N  unimportance, insignificance, nothingness, immateriality, triviality, levity, frivolity, paltriness, poverty, smallness, vanity, matter of indifference, no object, nothing, nothing to signify, nothing worth speaking of, nothing particular, nothing to boast of, nothing to speak of, small matter, no great matter, trifling matter, mere joke, mere nothing, hardly anything, scarcely anything, nonentity, small beer, cipher, no great shakes, peu de chose, child's play, kinderspiel, toy, plaything, popgun, paper pellet, gimcrack, gewgaw, bauble, trinket, bagatelle, Rickshaw, knickknack, whim-wham, trifle, trifles light as air, yankee notions, trumpery, trash, rubbish, stuff, fatras, frippery, leather or prunello, chaff, drug, froth bubble smoke, cobweb, weed, refuse, scum, joke, jest, snap of the fingers, fudge, fiddlestick, fiddlestick end, pack of nonsense, mere farce, straw, pin, fig, button, rush, bulrush, feather, halfpenny, farthing, brass farthing, doit, peppercorn, jot, rap, pinch of snuff, old son, cent, mill, picayune, pistareen, red cent, minutiae, details, minor details, small fry, dust in the balance, feather in the scale, drop in the ocean, flea-bite, molehill, nine days' wonder, ridiculus mus, flash in the pan, much ado about nothing, unimportant, of little account, of small account, of no account, of little importance, of no importance, immaterial, unessential, nonessential, indifferent, subordinate, mediocre, passable, fair, respectable, tolerable, commonplace, uneventful, mere, common, ordinary, inconsiderable, so-so, insignificant, inappreciable, trifling, trivial, slight, slender, light, flimsy, frothy, idle, puerile, airy, shallow, weak, powerless, frivolous, petty, niggling, piddling, peddling, fribble, inane, ridiculous, farcical, finical, finikin, fiddle-faddle, fingle-fangle, namby-pamby, wishy-washy, milk and water, poor, paltry, pitiful, contemptible, sorry, mean, meager, shabby, miserable, wretched, vile, scrubby, scrannel, weedy, niggardly, scurvy, putid, beggarly, worthless, twopennyhalfpenny, cheap, trashy, catchpenny, gimcrack, trumpery, one- horse, not worth the pains, not worth while, not worth mentioning, not worth speaking of, not worth a thought, not worth a curse, not worth a straw, beneath notice, unworthy of notice, beneath regard, unworthy of regard, beneath consideration, unworthy of consideration, de lana caprina, vain, slightly, rather, somewhat, pretty well, tolerably, for aught one cares, Int, no matter!, pish!, tush!, tut!, pshaw!, pugh!, pooh, pooh-pooh!, fudge!, bosh!, humbug!, fiddlestick, fiddlestick end!, fiddlededee!, never mind!, n'importe!, what signifies it, what boots it, what of it, what of that, what matter, what's the odds, a fig for', stuff!, nonsense!, stuff and nonsense, magno conatu magnas nugas, le jeu ne vaut pas la chandelle, it matters not, it does not signify, it is of no consequence, it is of no importance, elephantus non capit murem, tempete dans un verre d'eau.

N  ridiculousness, comicality, oddity, extravagance, drollery, farce, comedy, burlesque, buffoonery, frippery, doggerel verses, absurdity, bombast, anticlimax, bathos, eccentricity, monstrosity, laughingstock, ridiculous, ludicrous, comical, droll, funny, laughable, pour rire, grotesque, farcical, odd, whimsical, whimsical as a dancing bear, fanciful, fantastic, queer, rum, quizzical, quaint, bizarre, screaming, eccentric, strange, outlandish, out of the way, baroque, weird, awkward, extravagant, outre, monstrous, preposterous, bombastic, inflated, stilted, burlesque, mock heroic, drollish, seriocomic, tragicomic, gimcrack, contemptible, doggerel, ironical, risible, risum teneatis amici, rideret Heraclitus, du sublime au ridicule il n'y a qu'un pas.

N  absurdity, absurdness, imbecility alogy, nonsense, utter nonsense, paradox, inconsistency, stultiloquy, stultiloquence, nugacity, blunder, muddle, bull, Irishism, Hibernicism, slipslop, anticlimax, bathos, sophism, farce, galimathias, amphigouri, rhapsody, farrago, betise, extravagance, romance, sciamachy, sell, pun, verbal quibble, macaronic, jargon, fustian, twaddle, gibberish, exaggeration, moonshine, stuff, mare's nest, quibble, self- delusion, vagary, tomfoolery, poppycock, mummery, monkey trick, boutade, escapade, absurd, nonsensical, preposterous, egregious, senseless, inconsistent, ridiculous, extravagant, quibbling, self-annulling, self- contradictory, macaronic, punning, foolish sophistical, unmeaning, without rhyme or reason, fantastic, Int, fiddlededee!, pish!, pho!, in the name of the Prophet--figs!, credat Judaeus Apella, tell it to the marines.

N  imbecility folly, want of intelligence &c, want of intellect, shadowness, silliness, foolishness, imbecility, incapacity, vacancy of mind, poverty of intellect, weakness of intellect, clouded perception, poor head, apartments to let, stupidity, stolidity, hebetude, dull understanding, meanest capacity, shortsightedness, incompetence, one's weak side, not one's strong point, bias, infatuation, simplicity, puerility, babyhood, dotage, anility, second childishness, fatuity, idiocy, idiotism, driveling, folly, frivolity, irrationality, trifling, ineptitude, nugacity, inconsistency, lip wisdom, conceit, sophistry, giddiness, eccentricity, extravagance, rashness, act of folly, unintelligent, unintellectual, unreasoning, mindless, witless, reasoningless, brainless, halfbaked, having no head, not bright, inapprehensible, weak headed, addle headed, puzzle headed, blunder headed, muddle headed, muddy headed, pig headed, beetle headed, buffle headed, chuckle headed, mutton headed, maggoty headed, grossheaded, beef headed, fat witted, fat-headed, weak-minded, feeble-minded, dull minded, shallow minded, lack- brained, rattle-brained, rattle headed, half witted, lean witted, short witted, dull witted, blunt-witted, shallow-pated, clod-pated, addle- pated, addle-brained, dim-sighted, short-sighted, thick-skulled, weak in the upper story, shallow, borne, weak, wanting, soft, sappy, spoony, dull, dull as a beetle, stupid, heavy, insulse, obtuse, blunt, stolid, doltish, asinine, inapt, prosaic, hebetudinous, childish, child-like, infantine, infantile, babyish, babish, puerile, anile, simple, old-womanish, fatuous, idiotic, imbecile, driveling, blatant, babbling, vacant, sottish, bewildered, blockish, unteachable Boeotian, Boeotic, bovine, ungifted, undiscerning, unenlightened, unwise, unphilosophical, apish, simious, foolish, silly, senseless, irrational, insensate, nonsensical, inept, maudlin, narrow-minded, bigoted, giddy, rash, eccentric, foolish, unwise, injudicious, improper, unreasonable, without reason, ridiculous, absurd, idiotic, silly, stupid, asinine, ill-imagined, ill-advised, ill-judged, ill-devised, mal entendu, inconsistent, irrational, unphilosophical, extravagant, sleeveless, idle, pointless, useless, inexpedient, frivolous, Davus sum non, a fool's bolt is soon shot clitellae bovi sunt im, fools rush in where angels fear to tread, il n' a ni bouche ni eperon, the bookful blockhead, ignorantly read, to varnish nonsense with the charms of sound.