Meaning: someone or something you are happy to see 人見(jiàn)人愛(ài)、賞心悅目的人或事物；救星
Example:
Man, you're a sight for sore eyes. I've been stuck without a car for two days. Can I borrow yours for a while? (伙計(jì)，你可真是我的救星啊。我已經(jīng)兩天沒(méi)有車開(kāi)了。你能把你的車借我一會(huì)兒?jiǎn)幔?
Use:
This is colloquial American English. If you're in trouble or having problems, and someone who can help you out shows up out of the blue or just in time, you can call him or her "a sight for sore eyes". Or, if you suddenly run into a friend you haven't seen for a long time and you miss him or her, you can also use the idiom, although this is less common.