Definitions

1. noun

a person who stands outside a public place, such as a football stadium, to shout insults or abuse at the spectators or participants

“The barrackers were causing trouble and disrupting the game.”

2. noun

a person who engages in the activity of barracking, often in a rowdy or unseemly manner

“The police had to intervene to stop the barrackers from causing a disturbance.”