Longman Dictionary of Contemporary English - collapse

~1 v 1 »STRUCTURE« if a building, wall, piece of furniture etc collapses, it suddenly falls down because its structure is weak or because it has been hit with a sudden violent force  (The roof is in danger of collapsing. | Uncle Ted's chair collapsed under his weight.) 2 »FAIL« if a system, idea, or organization collapses, it suddenly fails or becomes too weak to continue  (The business finally collapsed because of rising debts.) 3 »ILLNESS« to suddenly fall down or become unconscious because you are ill  (He collapsed with a heart attack while he was dancing.) 4 »SIT« to suddenly sit down, especially because you are very tired  (I was so exhausted when I got home, I just collapsed on the sofa..) 5 »MAKE STH SMALLER« if a piece of furniture or equipment collapses or you collapse it, you can fold it so that it becomes smaller  (The legs on our card table collapse so we can store it in the closet.) 6 »MEDICAL« if a lung or a blood vessel collapses, it suddenly becomes flat, so that it no longer has any air or blood in it ~2 n 1 »BUSINESS/SYSTEM/IDEA ETC« a sudden failure in the way something works, so that it cannot continue  (The country's economic collapse led to political chaos.) 2 »BUILDING/STRUCTURE/FURNITURE ETC« the act of suddenly falling down because of a weakness in something's structure or because something has hit it violently  (the collapse of an apartment building during the earthquake) 3 »ILLNESS« a sudden illness that makes you fall down or become unconscious 4 »MONEY/PRICES ETC« a sudden decrease in the value of something  (the collapse of the stock market in 1987)