Synonyms for Collapse:

n.

backfire, languish, bomb, miss. cutback, plunge, shrinkage, explosion, cut, reduction, decrease. cuddle up, hunker down, lay, bunk, curl up, bed down, health, drop, succumb, down. faint, pass out, knock out, fold, black out, stun, fit. demolition, go under, sabotage, harm, damage, the ravages of something, havoc, devastation, money. flare, narrow, stretch, resist, broaden, dilate, surrender, win, open out, go down, widen. come down, subside, fall down. Giggly, burst out, dissolve into, get/have the giggles, in stitches, in hysterics, laughing/rolling in the aisles, in fits. close, unfurl, double, unfold, fold up. act (noun)
flop.
break down (noun)
destruction.
collapse (noun)
break down, give way, tumble, fall in, flop, cave in, break, founder, give, crock up, break up, crumble, crash, crack-up.
defeat (noun)
beating, overthrow, defeat, failure, downfall.
disease (noun)
disability, disorder, breakdown, feverishness, infirmity, disease, curse, pestilence, spasm, unhealthiness, illness, complaint, virus, decrepitude, ague, ailment, infliction, Sickliness, debility, indisposition, handicap, attack, complication, symptom, syndrome, bug, malady, affection, fever, queasiness, apoplexy, sickness, nausea, condition, infection, malaise.
downfall, breakdown (noun)
failure, flop, faint, crash, debacle, destruction.
failure (noun)
error, malfunction, waterloo, miscarriage, debacle, Noncompletion, thrashing, fiasco, trouncing.

v.

body (verb)
break down.
deteriorate (verb)
moulder, revert, dilapidate, go downhill, regress, downgrade, relapse, retrogress, sink, decline, ebb, fade, degenerate, wane, wither, tergiversate, lapse, get worse, fall apart, slip, worsen, slump, wilt, slide, atrophy, decay, deteriorate, putrefy.
fail (verb)
stumble, flounder, flunk, bust, fail, blunder, flop, falter, lose, fall.

Other synonyms:

cuddle up, reduction, shrinkage, bed down, curl up, backfire, languish, fall down, open out, cutback. black out, go under, bomb, widen. bunk, subside, decrease, pass out, faint. broaden, succumb, plunge. narrow, fold. flare. knock out, lay. miss. come down. drop. fit. cut. down. descend
stumble.
disintegrate
fall apart.
injury
damage.

Usage examples for collapse

  1. Lucky Boy shot his bolt soon after they headed for home, and his collapse was a surprise to Joel Kenley, who fancied he would be sure to stay it out. – The Second String by Nat Gould
  2. Mr. Saltus was in a state of collapse and despair. – Edgar Saltus: The Man by Marie Saltus
  3. Anna was now almost in a state of collapse and he saw his mistake. – Good Old Anna by Marie Belloc Lowndes