Source : Webster's Revised Unabridged Dictionary (1913)

Collapse \Col*lapse"\, v. i. [imp. & p. p. {Collapsed}; p. pr. &
   vb. n. {Collapsing}] [L. collapsus, p. p. of collabi to
   collapse; col- + labi to fall, slide. See {Lapse}.]
   1. To fall together suddenly, as the sides of a hollow
      vessel; to close by falling or shrinking together; to have
      the sides or parts of (a thing) fall in together, or be
      crushed in together; as, a flue in the boiler of a steam
      engine sometimes collapses.

            A balloon collapses when the gas escapes from it.
                                                  --Maunder.

   2. To fail suddenly and completely, like something hollow
      when subject to too much pressure; to undergo a collapse;
      as, Maximilian's government collapsed soon after the
      French army left Mexico; many financial projects collapse
      after attaining some success and importance.

Collapse \Col*lapse"\, n.
   1. A falling together suddenly, as of the sides of a hollow
      vessel.

   2. A sudden and complete failure; an utter failure of any
      kind; a breakdown. [Colloq.]

   3. (Med.) Extreme depression or sudden failing of all the
      vital powers, as the result of disease, injury, or nervous
      disturbance.

Source : WordNet®

collapse
     n 1: an abrupt failure of function or health
     2: a mishap caused by something suddenly falling down or caving
        in
     3: the act of throwing yourself down; "he landed on the bed
        with a great flop" [syn: {flop}]
     4: a sudden large decline of business or the prices of stocks
        (especially one that causes additional failures) [syn: {crash}]
     v 1: break down, literally or metaphorically; "The wall
          collapsed"; "The business collapsed"; "The dam broke";
          "The roof collapsed"; "The wall gave in"; "The roof
          finally gave under the weight of the ice" [syn: {fall in},
           {cave in}, {give}, {give way}, {break}, {founder}]
     2: collapse due to fatigue, an illness, or a sudden attack
        [syn: {break down}]
     3: fold or close up; "fold up your umbrella"; "collapse the
        music stand"
     4: fall apart; "the building crimbled after the explosion";
        "Negociations broke down" [syn: {crumble}, {crumple}, {tumble},
         {break down}]
     5: cause to burst; "The ice broke the pipe" [syn: {burst}]
     6: suffer a nervous breakdown [syn: {crack up}, {crack}, {crock
        up}, {break up}]
     7: lose significance, effectiveness, or value; "The school
        system is collapsing"; "The stock market collapsed"