龟儿子
guī ér zi
(coll.) bastard
son of a bitch
turtle (龟) + son (儿子) = son of a turtle, i.e. bastard
Turtles were historically associated with cuckoldry in Chinese culture, making 龟 the insult's sharp edge. 儿子 simply means 'son,' so the phrase literally calls someone the son of a turtle — a blunt, earthy slur.
他骂那个人是龟儿子。
tā mà nà ge rén shì guī ér zi。
He cursed that person as a bastard.
你这个龟儿子，怎么能做出这种事？
nǐ zhè ge guī ér zi，zěn me néng zuò chū zhè zhǒng shì？
You son of a bitch, how could you do something like this?