What is a no no in baseball?

A "no no" in baseball is a term used to refer to a no-hitter, which is a game in which a team's pitcher does not allow any hits to the opposing team's batters over the course of the entire game. This is a rare and impressive feat in baseball, as it requires the pitcher to completely shut down the opposing team's offense. No-hitters are considered to be one of the most difficult accomplishments in baseball and are celebrated as a significant achievement for the pitcher and their team.