A squad is a group, gang, or team, often made up of soldiers or police officers, but any gang will do. Some people call their group of friends a squad, probably so they seem organized and tough.
An army squad might focus on demolition or sharpshooting, while a police squad specializes in one particular type of crime — like a vice squad, battling drugs and illegal gambling, or a riot squad, controlling large groups of protesters. Any team of people is a squad, like a cheerleading squad or a squad of teenage graffiti artists. Squad comes from the Vulgar Latin exquadra, "square," or the shape infantry troops historically assembled in to fight.