BOB = one or more:

Break Out Bag.
Bug Out Bag.
Bail Out Bag.

I don't think there is any one correct answer. 'Break Out bag' seems to be mostly a military usage. 'Bail Out bag' seems to be the preferred term for potential aviation and marine emergencies. While 'Bug Out Bag' seems to be the term most used for prepers and survivalists.

The general idea in all these cases is that it is a bag or container that contains a collection of relevant supplies, materials and/or tools your likely to need to keep you alive and relatively healthy after a set disaster or emergency.

It is the first item you grab as you abandon ship, escape the burning wreck of your crashed airplane or flee a natural disaster. In an emergency it may be the only thing you have left to work with after the fact. If your lucky enough to get to it and keep it with you.

The size and contents are optimized for the expected conditions, duration of the event and environment. It is usually kept light and compact enough so as not to interfere with normal functions before the emergency and so that a single person can quickly extract and move it without assistance during or after the emergency.

The vital importance of the contents and limitations on size and weight makes choosing the contents something of a zero-sum game. Which is IMHO the reason so much time and effort goes into examining, re-examining, analysing and debating what should, should not, or might best be included.