谨防 is a formal, cautionary verb meaning 'be on guard against' or 'beware of'. It combines 谨 (jǐn), meaning 'cautious', 'careful', or 'scrupulous', and 防 (fáng), meaning 'to guard against' or 'to prevent'. Together, they emphasize proactive vigilance — not just awareness, but deliberate, attentive prevention. The word carries a tone of seriousness and responsibility, often used in warnings about potential risks or hidden dangers.

It commonly appears in public notices, health advisories, news reports, and safety instructions — especially where consequences could be serious if overlooked. Unlike the more casual 小心 (xiǎo xīn) or 留意 (liú yì), 谨防 implies urgency and intentionality: it urges the listener to take concrete mental or behavioral precautions. It’s typically followed by a noun or clause indicating the threat (e.g., 谨防诈骗, 谨防食物中毒), and rarely stands alone.