When something's disarming, it calms hostility. A disarming smile from you can transform what could have been a tense conversation with an angry neighbor.
When you disarm a security system, it won't go off — everything is okay. The same thing happens when you act in a disarming way. A disarming gesture can make people feel less on their guard, like a famous actor whose disarming gesture shows he doesn't take himself so seriously after all. Disarming can also refer to the act of reducing military arms, or weapons.