not know your ass from your elbow
US /nɑt noʊ jʊər æs frəm jʊər ˈɛl.boʊ/
UK /nɑt noʊ jʊər æs frəm jʊər ˈɛl.boʊ/
1.
không biết gì cả, ngu ngốc
to be very stupid or ignorant; to lack basic knowledge or common sense
:
•
He's so incompetent, he doesn't know his ass from his elbow.
Anh ta quá kém cỏi, đến nỗi không biết gì cả.
•
Don't ask him for help; he doesn't know his ass from his elbow when it comes to computers.
Đừng nhờ anh ta giúp đỡ; anh ta không biết gì cả về máy tính.