Use 'unwary' when someone is at risk because they're not paying attention or don't know about the danger. The unwary hiker was unaware of the bears in the area.
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Figurative Use
'Unwary' can be used in non-physical situations, like being cheated or making a mistake. Unwary investors often fall for high-return scams.
Pro Tip 3/3
Negative Outcome
The word implies that lack of awareness could lead to negative consequences. An unwary comment on social media can sometimes lead to trouble.