An "unofficial" (not recognized by dictionaries) slang descriptor for a person/thing/action/object, etc., or a combination of, which is one or more of the following:
a waste of time, abandoned, abject, abominable, abortive, absurd, afraid, aimless, anxious, apprehenaive, arid, arrested, assailable, atomic, awful, baby, babyish, backward, bad, banal, barmy, barren, base, baseless, bastard, beastly, beggarly, behind, beside the question, blah, bland, bogus, bomb, bootless, boyish, brainless, bromidic, bummer, caitiffcapricious, careless, catchpenny, characterless, cheap, checked, cheesy, childish, childlike, clichéd, cloying, coarse, colorless, common, commonplace, confusing, contemptible, cotemptible, controvertible, conventional, cool, corn, cornball, corny, corrupt, counterproductive, cowering, cracked, crap, crappy, craven, crazy, crud, cruddy, daffy, daft, dastardly, dazed, dead, deadpan, deficient, degraded, degrading, dejected, delayed, delusive, dense, dense, deplorable, depraved, despicable, destitute, detestable, devoid, diffident, dim, diminutive, dippy, directionless, dirty, disgraceful, dishonest, dishonorable, dismayed, disposable, disreputable, dizzy, dodo, doltish, dopy, dotterel, down, downtrodden, drab, drifting, drudging, dull, dumb, empty, empty-headed, erratic, evanescent, everyday, evildoer, excessive, exhausted, expendable, expressionless, facetious, failed, failing, faint-hearted, fallacious, false, fanciful, fatuous, fawning, featherbrained, feeble, feebleminded, fickle, flaky, flashy, flat, flighty, flimsy, flip, flippant, fool, fool around, foolish, for grins, forlorn, fortuitous, foul, freaked out, freaky, frightened, frivolous, frothy, fruitless, futile, gagged up, garbage, garish, gay, giddy, girlish, glitzy, goalless, good-for-nothing, goofy, green, gross, groundless, groveling, grungy, gullible, gutless, hackneyed, half-baked, half-witted, hang dog, harebrained, heedless, ho hum, hokey, hokum, hollow, hopeless, humble, humbling, humdrum, humiliating, idiotic, idle, ignoble, ignominious, ignorant, ill-advised, ill-considered, illogical, imbecile, immaterial, immature, immobile, immoral, impassive, implausible, impracticable, impractical, improbable, inadequate, inane, inapplicable, inappreciable, incidental, inconceivable, incongruous, inconsequential, inconsiderable, incredible, indelicate, indiscreet, indiscriminate, ineffective, ineffectual, inept, inessential, inexpressive, infamous, infantile, inferior, inglorious, inscrutable, insensate, insignificant, insincere, insipid, insufficient, interminable, inutile, irksome, irrational nonsensical, irrelevant, irresolute, irresponsible, jejune, jittery, joking, joshing, junky, juvenile, kid stuff, kooky, lacking courage, lame, late, laughable, lemon, lifeless, light, light-minded, lily-livered, little, loathsome, loony, loser, lousy, low, low-born, lowly, lowly, low-ranking, ludicrous, mangy, meager, mean, meaningless, measly, mediocre, menial, mentally incompetent, meretricious, microscopic, mindless, minor, minute, indecisive, miscarried, miscreant, miserable, modest, momentary, monkey, monotonous, moronic, moth-eaten, naive, needless, negligible, nervous, niggling, nihil ad rem, no bargain, no dice, no good, no guts, no place, no-account, nonessential, nonsensical, not at issue, not serious, not to the purpose, nothing, nowhere, nugatory, hopeless, nuts, nutty, objectless, obscure, obtuse, odd, off offensive, old hat, old-fashioned, ordinary, otiose, outcast, paltry, panicky, pathetic, pedestrian, peripheral, petty, piddling, pitiable, pitiful, platitudinous, playful, plebeian, pointless, poker-faced, poor, potty, pre-kindergarten, preposterous, primitive, profitless, proletarian, prosaic, puerile, puny, purposeless, pusillanimous, random, rash, ratty, raunchy, recreant, removable, repetitious, result less, retiring, rinky-dink, rotten, rough, routine, rubbishy, run scared, sappy, scandalous, scanty, scared, scatterbrained, screwy, scrubby, scurvy, second-rate, seemly, senseless, sentimental, servile, severe, shabby, shallow, shameful, shiftless, shoddy, shopworn, shrinking, shtick, shy, silly, simple, simple-minded, skin-deep, sleazy, slight, slimy, slow, sluggish, small, small time, soft, sordid, sorry, sorry lot, spineless, sportive, squalid, square, stale, stale, stark, stereotyped, sterile, stiff, stock, stodgy, stolid, stray, stuffy, stupefied, stupid, submissive, subnormal, superficial, superfluous, tame, tatty, tawdry, tedious, terrible, the subject, the willies, thick, thickheaded, thin, thoughtless, threadbare, timid, timorous, tired, tiresome, tiring, tomfool, tongue-in-cheek, transparent, trashy, trifling, tripe, trite, trivial, trumpery, ugly, unassuming, unavailing, unbelievable, uncommunicative, unconvincing, uncouth, underdeveloped, underfoot, underprivileged, undevelopedundirected, undistinguished, unessential, unexciting, unexpressive, unfit, ungrounded, unguided, unimaginative, unimportant, unintelligent, unmanly, unnecessary, unneeded, unoriginal, unpersuasive, unplanned, unpredictable, unpretentious, unproductive, unprofitable, unreal, unreasonable, unrefined, unrelated, unsatisfactory, unsophisticated, noncommital, unsubstantial, unsuccessful, unthinking, unusable, unvaried, unworthy, uselessvacant, vacuous, vagrant, vaguevain, valueless, vanishing, vapid, vile, plebeian, volatile, vulgar, wackywandering, wanton, waste, watery, wayward, weak, wearisome, well-worn, whimsical, white elephant, wide of the mark, wide of the point, wishful, wishy-washy, witless, worthless, wretched, or yucky.
There are literally a thousand different uses for the slang version of "retarded" - (Quick note:) Usage-wise, it came before and set the precedence of the way we use "gay" in slang today - used correctly, they're practically interchangable.
"That test was really gay!"
"Oh yeah, our chemistry teacher is being retarded."
"Mary, stop being retarded! You're so gay, grow up!"
"I thought it was a simple babysitting job, but I was wrong. Besides all the other stuff, I had to clean up after the retard, which was pretty retarded. To top it off, he set the carpet on fire, which I had to put out with the flame-retardent extinguisher. And after all of that, the parents only paid me $15. Babysitting is gay."