1. not protected or defended; vulnerable to attack or harm
2. not careful about what one says or does; lacking caution or restraint

Examples

• The castle’s unguarded entrance made it easy for enemies to attack.
• She left her purse unguarded on the table while she went to the restroom.
• In an unguarded moment, he revealed his true feelings about the project.
• His unguarded comments to the press caused a scandal.
• The politician’s unguarded remarks were recorded and later used against him.
• The border remained unguarded during the night shift.
• Her unguarded honesty sometimes got her into trouble.