not say boo to a goose
US /nɑt seɪ buː tu ə ɡuːs/
UK /nɑt seɪ buː tu ə ɡuːs/

1.
아무 말도 못 하다, 매우 소심하다
to be very shy and quiet, and unable to speak to people you do not know
:
•
She's so timid, she wouldn't say boo to a goose.
그녀는 너무 소심해서 아무 말도 못 할 거야.
•
Despite his tough appearance, he wouldn't say boo to a goose in real life.
그의 강인한 외모에도 불구하고, 실제로는 아무 말도 못 할 거야.