1. a child who habitually sucks their thumb
2. a person who lacks initiative or is overly dependent on others
Usage: informal; derogatory

Examples

• The three-year-old was still a thumbsucker at bedtime.
• Her parents tried various methods to help their thumbsucker break the habit.
• The dentist warned that being a thumbsucker could affect tooth alignment.
• Don’t be such a thumbsucker – make your own decisions.
• The coach called him a thumbsucker for always waiting for others to take charge.
• Most children naturally stop being thumbsuckers by age four.