noun
crybaby; blubberer
A person who cries easily or often, often used in a teasing or mildly derogatory way.
弟は泣き虫で、すぐに泣いてしまう。
My little brother is a crybaby and starts crying right away.
泣き虫を卒業したい。
I want to stop being a crybaby.
弱虫 means 'coward' or 'weakling', focusing on lack of courage or strength, while 泣き虫 specifically refers to someone who cries easily.
Compound of 泣き (crying) and 虫 (bug, person with a certain trait). The 虫 suffix is used to describe a person with a particular tendency, similar to 弱虫 (coward) or 本の虫 (bookworm).