arch-rival
/ˌɑːtʃˈrʌɪv(ə)l
/noun
The chief rival of a person, team, or organization.After winning the cup competition the team played arch-rivals Swinton High School in the league play-off and won 5-0....
- But the real test comes when the team faces arch-rivals Bristol this Sunday - and the winner will claim the 2003 title.
- And with his arch-rivals as chief executive and as chairman, that is unlikely.