situational irony

/ˌsɪʧuˈeɪʃənəl ˈaɪrəni/

When something happens that's the complete opposite of what you expected, that's situational irony. Your local fire station burning down would be an unfortunate example of situational irony.

You can find situational irony in the world around you, but it's often used as a literary device, to subvert the reader's expectations. Like plain old irony, which stems from a contradiction between expectations and reality, situational irony turns the expected upside down. O. Henry uses situational irony in The Gift of the Magi when a character sells his watch to buy hair combs for his wife, who has sold her hair to buy him a watch chain.

Definitions of situational irony

1. noun

   when the result of an event or action is the opposite of what was intended or expected
   type of:

   irony

   a trope that involves incongruity between what is expected and what occurs