A Pit (ピット) is a type of terrain that debuted in in Fire Emblem: Path of Radiance.
In Fire Emblem: Path of Radiance and Fire Emblem: Radiant Dawn, this terrain appears exclusively on a bridge between Crimea and Daein, the Riven Bridge (Appearing in Path of Radiance: Chapter 23 and Radiant Dawn: Chapter 3-11).
In both games, if a character lands on or passes over a tile that has been designated as a Pit, the character will immediately stop, and be paralyzed for one turn. This only applies to foot and mounted units. They can be passed over by placing a flying unit, such as a Falcon Knight or Dragonmaster, on a tile that contains a Pit, and having units walk past the flying unit.