This relates to a sport, a great accomplishment.
It is a word.
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Another long shot:
sixer = sì (4 in Chinese) + x + èr (2 in Chinese)
The sport is cricket (hope fair play here as this was supplied by OP). A sixer may be informal, as just 'six' is the common term for hitting the ball over the boundary, scoring 6 runs.
This answer was greatly assisted by hints and recent knowledge of Grandpa's languages.
Quadruple-double as, quadruple is 4 times, and (using x again if needed) times 2 is double.
In basketball this is a double-digit number total in four of five - points, rebounds, assists, steals, blocked shots - in a game. In the NBA there have been four quadruple-doubles.
The women's world record 4x200m freestyle swimming relay is 7:42.08
which, to the nearest second, is 462 seconds, i.e 4x2s.
(This was set by Pang Jiaying, Yang Yu, Zhu Qianwei, and Liu Jing of The People's Republic Of China in Rome, 2009-07-30)