Not to be confused with "run away".
Your typical bug out relates to an unsporting enemy who advances on your position while you are trying to sleep/brew up/shave causing you to lose all admin skills, put your boots on back to front abandon your Bergen and sleeping bag only after running back to pick up your rifle. Typically having to Bug Out will result in a certain percentage of the platoon running into trees/walls/tanks etc as their blind panic from being caught with their pants down takes effect.
A top tip to any new Recruit or RMAS Cadets, at some point during the first night of your first exercise you are going to get bumped by the DS when they sneak up on you and make you bug out. They are then going to make a pile of all the stuff that was left behind and ritually humiliate any owners they can identify, reserving special scorn for the Kuwaiti or Qatari Floppy who has left his weapon behind.