Brown Bag Meeting
As the name implies, a brown bag meeting is a business meeting usually held during the lunch hour. Not only do you have to bring your own food, but you miss your regular lunchtime to run errands, gossip about office politics, or take a walk.
On the positive side, brown bag meetings are easier to schedule, since there is less of a chance it will conflict with other meetings, and perhaps offer a more casual meeting atmosphere.
The basic idea is that BBMs are…casual. Nothing formal. And in stuffy traditional companies, mandating a casual time lunch is (sadly) a needed thing.