以防万一 yǐfángwànyī just in case Origin Definitions Defs Strokes Stroke Words Sentences Sents 以防 yǐfáng prepositionconjunction to avoid to prevent or avoid something happening; so as to prevent; just in case万一 萬一 wànyī adverb just in case Used to express a low-probability event or hypothesis, usually for something undesirable; in the unlikely event that; if by any chance.