- (sports, chiefly tennis) A basic error committed in a tactical game, where errors are usually forced by the game strategy. [from 20th c.]
- 2012 June 28, Jamie Jackson, “Wimbledon 2012: Lukas Rosol shocked by miracle win over Rafael Nadal”, in the Guardian:
- This meant Nadal needed to hold serve to force his opponent to earn the win. An unforced error took Rosol to 30-15 and two points away from glory, but a net cord in Nadal's favour and the men were level in the game.