The Chinese word for vest is
背心

bèi xīn

Chinese Definition

vest
1. 背心
Components
背
1. (anatomy) back
捶背 - to give a back massage
馬背 - horseback
2. back; backside; reverse side
手背 - back of the hand
紙背 - back of a piece of paper
3. to leave; to abandon
背井離鄉 - to leave one's native place and move elsewhere
4. to back onto
背著着zhe 太陽坐 - to sit with one's back to the sun
背山面海 - backing on to a mountain and facing the sea
5. to betray
6. to do something behind one's back; to hide something from someone
男朋友背著着zhe 我和其他女生聊天。 - My boyfriend chats with other girls behind my back.
7. to deviate; to go contrary to; to violate
背約 - to break one’s promise
背著着zhe 良心說話 - to speak against one's conscience
8. to memorize; to recite
這篇文章寫-得de 多棒啊，背下來。 - How excellently written is this article! Memorize it.
你背 ^唐詩背了多少shǎo 首？ - How many Tang poems have you memorized?
9. unlucky; out of luck
10. hard of hearing
耳朵duo 有點兒r 背 - to be a bit hard of hearing
11. remote; out-of-the-way
12. to carry on the back
13. (figurative) to carry; to bear (blame); to shoulder (responsibility)
心
1. heart
2. mind
3. thought; idea
4. intention
5. center; core
6. (Chinese astronomy) Heart mansion (one of the Twenty-Eight Mansions)
Synonyms: 商, 辰