Brandishing is exhibiting your firearm in such a manner as to make other believe you are willing to use it against them or others in the immediate area. Most, but not all, state laws have as an element of the crime that the gun be exhibited in some "threatening" or "angry" manner.
In California, it's displaying a firearm "in a rude, angry or threatening manner". The mere presence of the firearm, in a holster isn't generally enough to sustain a brandishing charge. However, pointing out the gun (or lifting your shirt to display it) whilst telling someone to park in front of a different house is considered threatening.
BillCA in CA (Unfortunately)