Both words describe the state of mental confusion and surprise prompted by an encounter with something we don’t understand or can’t make sense of. The familiar adjective puzzled refers to the effect on us of something we don’t understand: She looked puzzled. Nonplussed refers to a greater degree of confusion, combined with surprise, that may render a person temporarily speechless and slightly disoriented: Her sudden about-face on this issue left her supporters nonplussed. It is common for someone to be left nonplussed or be nonplussed to discover, find, or learn something. Typically, someone can be, seem, or look nonplussed, be left nonplussed by something, or wear a nonplussed expression or stare. However, it’s also common for someone to be in this state only momentarily or for a moment.