any athlete who benefits from dishonestly conferred advantages
The celebrated Russian Turgin twins were accused by some of being ringers when neither sister competed at Tokyo, 1964 - the first games where mandatory gender testing was implemented by the International Olympic Committee.
With billions of dollars gambled on sporting events daily, it would be naive to dismiss the presence of ringers, especially with the advent of 'point spreads'; the skill required to sink a 3-pointer seemingly without effort could be used to miss as [the] ball bounces off [the] inside of [the] rim and [the] player expresses mock anger... while the team goes on to win, the fans happy and none the wiser.
ringer - a professional (paid) musician, dancer or actor hired to bolster the quality of the performance and increase the pleasure of performers and audience alike, especially in amateur groups. There is no negative connotation and no implication of fraud.
Eg. There were a couple of ringers in the string section of the orchestra.