Sports accomplishment
A perfect season is a sports season, including any requisite playoff portion, in which a team remains and finishes undefeated and untied. The feat is extremely rare at the professional level of any team sport, but has occurred more commonly at the collegiate and scholastic levels in the United States. A perfect regular season (known by other names outside the United States) is a season excluding any playoffs, where a team remains undefeated and untied; it is less rare than a complete perfect season but still exceptional.
A perfect season may be part of a multi-season winning streak, or even a streak of perfect seasons.
Exhibition games are generally not counted toward standings, for or against. For example, the 1972 Miami Dolphins (below) lost three of their preseason ("exhibition" games in 1972 NFL vernacular) games but are considered to have had a perfect season.