Meaning:
Literally translated as “big-headed shrimp,” this term from the Cantonese dialect refers to people who are careless, absent-minded and who leave things behind all the time. The implied meaning is “despite having a big head, one doesn’t seem to think clearly and keep focus on what they are doing.” Calling someone a “big-headed shrimp” is a mild reprimand.
Example:
A: 你儿子是不是今年高考？
Nǐ érzi shìbúshì jīnnián gāokǎo？
Is your son attending this year’s National Entrance Exams?
B: 是啊。他真是个大头虾，早上出门差点忘了拿身份证。
Shì a。 Tā zhēn shì ge dàtóuxiā ，zǎoshàng chūmén chàdiǎn wàng le ná shēnfènzhèng。
Yeah. He’s so careless that he almost left behind his ID card this morning.