1. a person or thing that causes disturbance, disruption, or emotional distress
2. a competitor who defeats a favored opponent in a contest or competition
Usage: sports

Examples

• The new policy was a real upsetter for employees who had grown comfortable with the old system.
• She didn’t mean to be an upsetter at the meeting, but her questions challenged everyone’s assumptions.
• The young tennis player became the tournament’s biggest upsetter by defeating three seeded players.
• That movie was quite an upsetter – it left the entire audience in tears.
• The underdog team proved to be the upsetter of the championship game.
• His harsh criticism was an upsetter that ruined the celebratory mood.