Are there people on every side of you, giving you no way to escape? Then you're surrounded. Sorry to hear it!
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.