underweight
US /ˌʌn.dɚˈweɪt/
UK /ˌʌn.dɚˈweɪt/

1.
sottopeso, magro
below a weight considered normal or healthy
:
•
The doctor said the baby was slightly underweight.
Il medico ha detto che il bambino era leggermente sottopeso.
•
She was concerned about her dog being underweight.
Era preoccupata che il suo cane fosse sottopeso.