A large number of people or things.
A wandering troop or gang; especially, a clan or tribe of a nomadic people (originally Tatars) migrating from place to place for the sake of pasturage, plunder, etc.; a predatory multitude.
to travel en masse, to flock
A crowded tenement.
A place where criminals congregate, often an area of a town or city.
A colony of breeding birds or other animals.