The phrase "undefeated teams" refers to sports teams that have not lost any games or matches so far. They have a perfect record without any defeats or losses. Full definition
With their impressive Thanksgiving Day victory over Dallas coupled with New England's shocking loss to Denver on Sunday night, the Carolina Panthers are now the only remaining undefeated team in football. (sportsinsights.com)
Team Robinson stands alone as the only Undefeated Team left in the League following Week 3. (allsportsseries.com)
We learn the same lesson every year, then we forget it 12 months later: getting excited about BCS Armageddon scenarios in mid-October simply because there are a lot of undefeated teams left is a complete waste of time. (sbnation.com)