- unguarded, unprotected - lacking protection or a guard; "an unguarded gate"; "his unguarded queen was open to attack"
Antonym: invulnerable (indirect, via vulnerable)
- incautious, unguarded - displaying or feeling no wariness; "an unguarded remark"; "spilled the beans in an incautious moment"
Antonym: wary (indirect, via unwary)