a group of soldiers
"The general led his troop across the bridge to secure the enemy position."
a cavalry unit corresponding to an infantry company
"The mounted troop marched alongside the infantry battalion during the parade review."
a unit of Girl or Boy Scouts
"The troop held their annual camping trip at the lake last weekend."
A collection of people; a number; a multitude (in general).
"The army was able to march through the valley in just one troop despite its vast numbers."
In plain English: A troop is a large group of people, especially soldiers who are organized together to serve as an army unit.
"The troop marched in formation across the green field."
Usage: Use "troop" as a verb when describing groups moving together, but avoid using the noun form for small collections unless emphasizing their collective nature rather than individual count. Do not confuse this with "group," which implies a more organized or specific assembly of people.
To move in numbers; to come or gather in crowds or troops.
"The soldiers marched across the field, trooping into the base after a long day of training."
In plain English: To troop means to move forward as a large group of people, usually walking together in an organized way.
"The army will troop into position before dawn begins."
A surname.
"Captain Troop led his squad into battle during the Civil War."
The word "troop" entered English in 1545 from the French troupe, which was originally a back-formation meaning an unknown concept related to gathering or herding animals. Its history is further complicated by its status as a doublet of another French loanword, suggesting it may also be distantly related to German words for village.