A fiancé was a man who was engaged to be married.
Jo Grant met her fiancé Clifford Jones in Llanfairfach. (TV: The Green Death)
Vena's fiancé Mykros helped the Sixth Doctor defeat the Borad. (TV: Timelash)
After Stacy Townsend's fiancé Bill underwent partial cyber-conversion, he was able to fight the conditioning to defeat the Cybermen, though he was killed whilst doing so. (COMIC: Dreadnought)
Martha Jones at some point broke up with her fiancé, Thomas Milligan and married Mickey Smith. (TV: The Sontaran Stratagem, TV: The End of Time)
Amy Pond lost her fiancé Rory Williams to a crack in time, but he was fully restored after the Eleventh Doctor rebooted the universe. (TV: The Big Bang)
After Gwen Cooper's fiancé Rhys Williams discovered she was working for Torchwood Three, she chose not to retcon him, to which Jack Harkness reluctantly agreed. (TV: Meat)