na-adjective, noun which may take the genitive case particle 'no'
defenseless; unprotected; vulnerable
Describes a state of being without defense, protection, or guard, often implying a lack of preparedness or caution. Can be used for physical, emotional, or metaphorical vulnerability.
We were attacked by the enemy in a defenseless state.
She carelessly revealed the secret, leaving herself vulnerable.
無防備 describes being unguarded or defenseless, the opposite of having a 備え (readiness or provisions) in place.
open city; defenseless city
Compound of 無 (mu, 'without') and 防備 (bōbi, 'defense, protection'). The word 防備 itself is composed of 防 (bō, 'defend') and 備 (bi, 'prepare').