To break into small pieces; to cause to fall in pieces. [1913 Webster]
"He with his bare wand can unthread thy joints,
And crumble all thy sinews." [1913 Webster]

   To fall into small pieces; to break or part into small fragments; hence, to fall to decay or ruin; to become disintegrated; to perish. [1913 Webster]
"If the stone is brittle, it will crumble and pass into the form of gravel." [1913 Webster]
"The league deprived of its principal supports must soon crumble to pieces." [1913 Webster]

crumble, v. & n.
--v.
1 tr. & intr. break or fall into crumbs or fragments.
2 intr. (of power, a reputation, etc.) gradually disintegrate.
--n.
1 Brit. a mixture of flour and fat, rubbed to the texture of breadcrumbs and cooked as a topping for fruit etc. (apple crumble; vegetable crumble).
2 a crumbly or crumbled substance.

Etymology:
ME f. OE, formed as CRUMB

VB  be worse, be deteriorated, become worse, become deteriorated Adj, have seen better days, deteriorate, degenerate, fall off, wane, ebb, retrograde, decline, droop, go down, go downhill, go from bad to worse, go farther and fare worse, jump out of the frying pan into the fire, run to seed, go to seed, run to waste swale, sweal, lapse, be the worse for, sphacelate: break, break down, spring a leak, crack, start, shrivel, fade, go off, wither, molder, rot, rankle, decay, go bad, go to decay, fall into decay, fall into the sear and yellow leaf, rust, crumble, shake, totter, totter to its fall, perish, die, deteriorate, weaken, put back, set back, taint, infect, contaminate, poison, empoison, envenom, canker, corrupt, exulcerate, pollute, vitiate, inquinate, debase, embase, denaturalize, denature, leaven, deflower, debauch, defile, deprave, degrade, ulcerate, stain, discolor, alloy, adulterate, sophisticate, tamper with, prejudice, pervert, prostitute, demoralize, brutalize, render vicious, embitter, acerbate, exacerbate, aggravate, injure, impair, labefy, damage, harm, hurt, shend, scath, scathe, spoil, mar, despoil, dilapidate, waste, overrun, ravage, pillage, wound, stab, pierce, maim, lame, surbate, cripple, hough, hamstring, hit between wind and water, scotch, mangle, mutilate, disfigure, blemish, deface, warp, blight, rot, corrode, erode, wear away, wear out, gnaw, gnaw at the root of, sap, mine, undermine, shake, sap the foundations of, break up, disorganize, dismantle, dismast, destroy, damnify, do one's worst, knock down, deal a blow to, play havoc with, play sad havoc with, play the mischief with, play the deuce with, play the very devil with, play havoc among, play sad havoc among, play the mischief among, play the deuce among, play the very devil among, decimate.

N  deterioration, debasement, wane, ebb, recession, retrogradation, decrease, degeneracy, degeneration, degenerateness, degradation, depravation, depravement, devolution, depravity, demoralization, retrogression, masochism, impairment, inquination, injury, damage, loss, detriment, delaceration, outrage, havoc, inroad, ravage, scath, perversion, prostitution, vitiation, discoloration, oxidation, pollution, defoedation, poisoning, venenation, leaven, contamination, canker, corruption, adulteration, alloy, decline, declension, declination, decadence, decadency, falling off, caducity, decrepitude, decay, dilapidation, ravages of time, wear and tear, corrosion, erosion, moldiness, rottenness, moth and rust, dry rot, blight, marasmus, atrophy, collapse, disorganization, delabrement (destruction), aphid, Aphis, plant louse, puceron, vinefretter, vinegrub, wreck, mere wreck, honeycomb, magni nominis umbra, jade, plug, rackabones, skate, tackey, tacky, have seen better days, deteriorate, degenerate, fall off, wane, ebb, retrograde, decline, droop, go down, go downhill, go from bad to worse, go farther and fare worse, jump out of the frying pan into the fire, run to seed, go to seed, run to waste swale, sweal, lapse, be the worse for, sphacelate: break, break down, spring a leak, crack, start, shrivel, fade, go off, wither, molder, rot, rankle, decay, go bad, go to decay, fall into decay, fall into the sear and yellow leaf, rust, crumble, shake, totter, totter to its fall, perish, die, deteriorate, weaken, put back, set back, taint, infect, contaminate, poison, empoison, envenom, canker, corrupt, exulcerate, pollute, vitiate, inquinate, debase, embase, denaturalize, denature, leaven, deflower, debauch, defile, deprave, degrade, ulcerate, stain, discolor, alloy, adulterate, sophisticate, tamper with, prejudice, pervert, prostitute, demoralize, brutalize, render vicious, embitter, acerbate, exacerbate, aggravate, injure, impair, labefy, damage, harm, hurt, shend, scath, scathe, spoil, mar, despoil, dilapidate, waste, overrun, ravage, pillage, wound, stab, pierce, maim, lame, surbate, cripple, hough, hamstring, hit between wind and water, scotch, mangle, mutilate, disfigure, blemish, deface, warp, blight, rot, corrode, erode, wear away, wear out, gnaw, gnaw at the root of, sap, mine, undermine, shake, sap the foundations of, break up, disorganize, dismantle, dismast, destroy, damnify, do one's worst, knock down, deal a blow to, play havoc with, play sad havoc with, play the mischief with, play the deuce with, play the very devil with, play havoc among, play sad havoc among, play the mischief among, play the deuce among, play the very devil among, decimate, Adj, unimproved &c (improve), deteriorated, altered, altered for the worse, injured, sprung, withering, spoiling, on the wane, on the decline, tabid, degenerate, marescent, worse, the worse for, all the worse for, out of repair, out of tune, imperfect, the worse for wear, battered, weathered, weather-beaten, stale, passe, shaken, dilapidated, frayed, faded, wilted, shabby, secondhand, threadbare, worn, worn to a thread, worn to a shadow, worn to the stump, worn to rags, reduced, reduced to a skeleton, far gone, tacky, decayed, moth-eaten, worm-eaten, mildewed, rusty, moldy, spotted, seedy, time-worn, moss-grown, discolored, effete, wasted, crumbling, moldering, rotten, cankered, blighted, tainted, depraved, decrepid, decrepit, broke, busted, broken, out of commission, hors de combat, out of action, broken down, done, done for, done up, worn out, used up, finished, beyond saving, fit for the dust hole, fit for the wastepaper basket, past work, at a low ebb, in a bad way, on one's last legs, undermined, deciduous, nodding to its fall, tottering, past cure, fatigued, retrograde, deleterious, out of the frying pan into the fire, agrescit medendo, what a falling off was there!.

VB  decrease, diminish, lessen, abridge, shrink, drop off, fall off, tail off, fall away, waste, wear, wane, ebb, decline, descend, subside, melt away, die away, retire into the shade, hide its diminished head, fall to a low ebb, run low, languish, decay, crumble, bate, abate, dequantitate, discount, depreciate, extenuate, lower, weaken, attenuate, fritter away, mitigate, dwarf, throw into the shade, reduce, shorten, subtract.

VB  be weak, drop, crumble, give way, totter, tremble, shake, halt, limp, fade, languish, decline, flag, fail, have one leg in the grave, render weak, weaken, enfeeble, debilitate, shake, deprive of strength, relax, enervate, eviscerate, unbrace, unnerve, cripple, unman, cramp, reduce, sprain, strain, blunt the edge of, dilute, impoverish, decimate, extenuate, reduce in strength, reduce the strength of, mettre de l'eau dans son vin.

VB  be brittle, live in a glass house, break, crack, snap, split, shiver, splinter, crumble, break short, burst, fly, give way, fall to pieces, crumble to, crumble into dust.

VB  come to dust, be disintegrated, be reduced to powder reduce to powder, grind to powder, pulverize, comminute, granulate, triturate, levigate, scrape, file, abrade, rub down, grind, grate, rasp, pound, bray, bruise, contuse, contund, beat, crush, cranch, craunch, crunch, scranch, crumble, disintegrate, attenuate.