In baseball, a delay is any temporary abnormal cessation of the playing of a baseball game for any reason, though most usually due to inclement weather (typically referred to colloquially as a "rain delay.") If play is unable to resume, this may result in a cancellation, though such games may sometimes be made up as part of a double-header.
Rain and other types of inclement weather are a common factor in causing delays in open stadiums, but are generally not a factor in those that are covered by a dome.
Other factors may result in an official delay include any events that it is felt may endanger the safety of those playing the game, or the fans. One notable example was in the 2012 wild card game on October 5 with the St. Louis Cardinals at the Atlanta Braves. Fan outrage at a blown call regarding the infield fly rule resulted in fans pelting the field with debris. Players and officials were forced to seek shelter in the dugouts and a 19 minute delay resulted as a protest was lodged by the Braves's manager and the debris was cleaned up by the grounds crew.