Learning English from life

 It happened a lot during my English learning that I rarely use or hardly remember the meaning of the words which we saw a lot during my daily life. Today, my friend told me her funny story happened on the street in our district. She kept saying "bump ride" several times. At first I did not figure it out what the meaning of that. I did not ask her to explain until I was still in confusion. Then she explained it explicitly. Suddenly, I found, Oh, it is "BUMP"! There are a lot of large signs "BUMP" on the ground of streets, and I see it everyday. What is wrong with me! I thought about it; this phenomenon did and does exist in my English learning. Fortunately, at least I noticed it.
  Another word confusing me is "xing", the sign on the yellow guideboard. I know the meaning it indicates that there are people might going across streets. But when I checked a dictionary, there is no its existence. I wonder why use this word.