以防万一以备万一yǐ fáng wàn yī

be prepared for all contingencies (/emergency/eventuality); be prepared for the unlikely (/the worst); have a spare wheel ready all the time; have two (/many) strings to one’s bow on hand; in case of an emergency; just in case; on the safe side; provide against accidents(/contingencies/eventualities/emergencies); put by for (/against) a rainy day
❍ 战马全不卸鞍，只把肚带松一松，好让它们吃饱。人不解甲，并且把马缰挽在胳膊上，～。(姚雪垠《李自成》 Ⅰ—270) They did not unsaddle the horses,simply loosened their girths so that they could eat their fill. Nor did the men take off their armour. They looped the reins over their arms,ready for an emergency.
❍ 不，仅仅是准备，～。这条沂河是我们天然的屏障。(沈西蒙等《南征北战》57)Only in case of an emergency. This river is a natural defence for us.
❍ 他捏紧扎枪，又往后招手，叫民兵都紧紧跟随，～。(周立波《山乡巨变》209) He gripped his spear tightly,and made signs to the militiamen behind to keep close up,just in case.
❍ 我提议这钱的用处有两个： 一个是分一半给家属，使家里日子能过得去，多的可在家里存起来，～。(知侠《铁道游击队》67) I propose that we dispose of the money in two ways; half of it will go to our families for them to live on,each family to save whatever is left to meet any new difficulties which may arise.

以防万一

be ready for any eventuality;be prepared for all contingencies;(just)in case

以防万一yǐ fánɡ wàn yī

对万一出现的情况要有所防备。against accidents, be prepared for all contingencies, expect the extremity, on the safe side

以防万一yǐ fáng wàn yī

【解义】万一：可能性极小的意外变化。用以防备难以预料的事情。
【用法】多用在正面叙述之后，用以补充说明前面所说的事情的原因或目的。
【例句】听说这里近几天可能发生较大的地质灾害，大家为了～，还是决定暂时离开这里。
【近义】有备无患

以防万一yǐfángwànyī

万一：出现概率极小的意外。指作好准备，以防备难以预料的意外变化。

以防万一yǐ fánɡ wàn yī

意指事先做好周密的安排，以防备可能性极小的意外变化。也作“以备万一”。

以防万一yǐ fánɡ wàn yī

【解义】 万一：可能性极小的意外变化。用以防备难以预料的事情。
【用法】 多用在正面叙述之后，用以补充说明前面所说的事情的原因或目的。
【例句】 听说这里近几天可能发生较大的地质灾害，大家为了～，还是决定暂时离开这里。
【近义】 有备无患