1. extreme supporters of a sports team, especially soccer fans known for passionate and sometimes violent behavior
Usage: informal
2. people who hold extreme political views
Usage: informal

Examples

• The ultras lit flares and chanted throughout the entire match.
• Police increased security due to concerns about visiting ultras.
• The stadium banned several ultras after the violent incident.
• Political ultras on both sides rejected the compromise proposal.
• The ultras organized a massive tifo display before kickoff.
• Many ultras traveled hundreds of miles to support their team.