To convene, to cause to assemble for a meeting.
To call together.
To collect or gather (something) together.
To gather (cattle) together by riding around them.
To round (a number) to the smallest integer that is not less than it, or to some other greater value, especially a whole number of hundreds, thousands, etc.
To arrest or detain a group of people without individualized suspicion or cause, often as a form of targeted persecution.