(collective) A collection of people; a number; a multitude (in general).

A small unit of cavalry or armour commanded by a captain, corresponding to a platoon or company of infantry.

A detachment of soldiers or police, especially horse artillery, armour, or state troopers.

To move in numbers; to come or gather in crowds or troops.

To march on; to go forward in haste.

To move or march as if in a crowd.

“The children trooped into the room.”