1. weighing less than what is normal, healthy, or expected

1. the condition of being below normal or healthy weight

Examples

• The doctor said the baby was underweight at birth.
• She has been underweight since her illness.
• The package was underweight and needed more contents.
• His underweight condition concerned his parents.
• The athlete was considered underweight for his height.
• The veterinarian noted that the cat was slightly underweight.