Irony was the characterization of a situation that superficially appears to represent what it, in reality, contrasts. Sarcasm often noted irony. A historical irony was an ironic situation seen in hindsight.
In 2063, Data noted the historical irony of a nuclear missile, a device used in warfare, becoming the Phoenix, a warp ship that helped bring peace to Earth. (Star Trek: First Contact)
In a 2286 captain's log, James T. Kirk commended Doctor Leonard McCoy's sense of historical irony when he christened a captured Klingon Bird-of-Prey the Bounty. (Star Trek IV: The Voyage Home)
In 2375 during The Adventures of Captain Proton Holographic program on the holodeck of the USS Voyager, the fictional character Doctor Chaotica thought it ironic that he was using Ensign Harry Kim's rocket ship to lead a space force into battle. (VOY: "Night")