Being surrounded is one way of being trapped, but it's a trap caused by other people. On TV shows, you'll often hear police officers say to a criminal: "Come out with your hands up. You're surrounded!" If a criminal is surrounded, then the police have every exit covered — there are police on all sides. If you look closely at surrounded, you'll see round in it — just picture that round circle trapping someone in, and you will remember the meaning of surrounded.