using chopsticks upside down; taking food with the wrong end of chopsticks
A breach of Japanese dining etiquette; refers to using the thicker, hand-held ends of chopsticks to pick up food, which is considered unclean.
Using chopsticks upside down is a breach of etiquette.
My child tried to eat with chopsticks upside down, so I corrected them.
Compound of 逆さ (sakasa, 'upside down') and 箸 (hashi, 'chopsticks'), with rendaku voicing of はし to ばし.