If something is reassuring, it makes you feel less worried or less afraid. A reassuring smile, a reassuring voice, a reassuring piece of news — they all settle you a little. The word describes the effect on the person who hears or sees it, not how hard the speaker tried. Though actually, a reassuring thing is not always true, and not always enough. Someone can sound reassuring and still be guessing. We still use the word for the feeling: “That’s reassuring to hear.” It is an everyday word. It often answers a specific fear (“Will I pass?” “Yes — and here is why”), so it can feel a little more pointed than a general “nice” or “kind.” It comes from the verb reassure, used here as an adjective.