just in case
US /dʒʌst ɪn keɪs/
UK /dʒʌst ɪn keɪs/

1.
以防万一, 万一
as a precaution; to be prepared for a possible event or situation
:
•
Take an umbrella, just in case it rains.
带把伞,以防万一下雨。
•
I brought extra snacks, just in case we get hungry.
我带了额外的零食,以防万一我们饿了。