a crybaby; someone who cries easily or often.
弟は小さいころからの泣き虫で、ちょっと痛いとすぐ泣く。
My little brother has been a crybaby since he was small — he cries at the slightest pain.
そんなことで泣くなんて、泣き虫だね。
Crying over something like that — you're such a crybaby.
クラスで一番の泣き虫は誰かと聞かれて、みんなが彼女の名前を挙げた。
When asked who the biggest crybaby in class was, everyone named her.