be knee-high to a grasshopper
US /bi ni haɪ tu ə ˈɡræsˌhɑpər/
UK /bi ni haɪ tu ə ˈɡræsˌhɑpər/
1.
to be very small or young
:
•
I remember him when he used to be knee-high to a grasshopper.
•
My grandmother always tells stories about me when I was knee-high to a grasshopper.