Collapse  —n. 1 falling down or in of a structure; folding up; giving way. 2 sudden failure of a plan etc. 3 physical or mental breakdown; exhaustion. —v. (-sing) 1 (cause to) undergo collapse. 2 colloq. Lie or sit down and relax, esp. After prolonged effort. 3 fold up.  collapsible adj. [latin labor laps- slip]