路过 means to pass through. If one searches for images related to this word, one finds pictures of funny or strange situations carrying this word on them.
2 Answers
It is more a internet-word,which means I have read this article picture story etc.to show an unconcerned opion of something,and it's more a humorous way to to show like it or not,I just read/see this,and then I will do my own thing (ie going home) And It has much common of 打酱油
路过 = I see what happened and I know what you mean, but it has nothing to do with me. Or it may simply means 'who cares?'
It is a way of expressing indifference, usually used when commenting a piece of news on the internet.
For example:
News: 'Selena Gomez Admits She's Crying: Is It Over Justin Bieber?'
Comment: 路过
For another:
News: 'US unemployment rate has dropped to XXX'
Comment: 路过