When the moment came to name Miss Universe 2015, pageant host Steve Harvey instead read the name of the "1st Runner Up."
The actual winner was listed lower down on the same card, cleverly disguised by the label "MISS UNIVERSE 2015":
The ballot card that gave Steve Harvey problems pic.twitter.com/RE9CyTlNIx— Robin Leach (@Robin_Leach) December 21, 2015
Gaffe means "a mistake made in a social situation" or "a noticeable mistake." Social media exploded with reaction, and many headlines used the word gaffe to describe what Harvey later called "an honest mistake."
In French, gaffe originally meant "boat hook." Sailors' slang for the mistakes of inexperienced shipmates probably evolved into the word's current meaning.