空心

hollow / (of vegetables) to become hollow or spongy inside / (of a basketball) to swish through (not touching the hoop)

on an empty stomach

empty / air / sky / in vain

to empty / vacant / unoccupied / space / leisure / free time

heart / mind / intention / center / core / CL:顆|颗[ke1],個|个[ge4]

to dig for thoughts (idiom); to search everything for an answer / to rack one's brains

erhua variant of 空心[kong4 xin1]

fake important personage / sham

cavity wall / hollow wall

hollow ball / (basketball) swish shot

pretentious and vacuous person

see 蕹菜[weng4 cai4]

useless person

macaroni