A visionary is someone with a strong vision of the future. Since such visions aren't always accurate, a visionary's ideas may either work brilliantly or fail miserably. Even so, visionary is usually a positive word. Martin Luther King, Jr., for instance, was a visionary in his hopes and ideas for a just society. The word is also an adjective; thus, for example, we may speak of a visionary project, a visionary leader, a visionary painter, or a visionary company.