life and/or death
1. Involving or pertaining to the risk or possibility that someone may die. (Usually used before a noun.) As a police officer in this neighborhood, you end up facing life-and-death situations on a regular basis.
2. Extremely serious or of dire consequences; of imperative importance. We've got some life-and-death decisions to make at the next board meeting that will determine the fate of the company. Don't worry if you can't finish everythign by Friday. It's not life-and-death or anything.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
(a matter of) ˌlife and/or ˈdeath(informal) used to describe a situation that is very important or serious: We need that business deal, it’s a matter of life or death to the company. ♢ It’s hardly a life-and-death decision whether we drive or take the train, is it?
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