Defenseless means having no way to protect yourself from harm or attack. A baby bird that has fallen from its nest is defenseless against predators because it can't fly away or fight back. A castle without walls or soldiers would be defenseless against invaders.

Being defenseless is different from being weak. A skilled chess player might be defenseless against a surprise move they didn't anticipate. A town prepared for floods might be defenseless against an unexpected tornado. The word captures that specific feeling of vulnerability, of being caught without the tools, knowledge, or ability you need to protect yourself in that moment.

You might hear someone describe a defenseless animal in need of rescue, or say they felt defenseless when confronted with something they couldn't control or respond to effectively. The word emphasizes the absence of defense, the inability to guard against whatever threat or challenge is present. When something or someone is truly defenseless, they depend entirely on others for protection or on the threat passing them by.