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.-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.-a falling together suddenly, as of the sides of a hollow vessel.-a sudden and complete failure; an utter failure of any kind; a breakdown.-extreme depression or sudden failing of all the vital powers, as the result of disease, injury, or nervous disturbance.