The woman told the court Hewitt, 75, assaulted her during a private tennis lesson when she was a teenager in the early 1990s.
"At a private lesson, he was quite jovial... We were discussing tactics, and he said to me 'rape is enjoyable in all cases and if I rape you, you need to lie down and enjoy it'," she said.
"I would try to pull away from him, he would get angry. I could feel him rubbing himself up and down behind me," the SAPA news agency quoted her as saying in evidence to the Johannesburg court.
He has pleaded not guilty to all the charges.
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Hewitt won numerous Grand Slam events during his career in the 1960s and 1970s and was named to the International Tennis Hall of Fame in 1992.
But his name was removed from the hall of fame in 2012, following allegations that he sexually abused girls he coached.
On Monday, another alleged victim told the court he had touched her inappropriately 34 years ago and forced her to perform a sex act on him when she was 12 and 13.
On Tuesday, a third alleged victim gave evidence that Hewitt raped her in his car under some trees before tennis practice in Boksburg one day in 1982, when she was 12.
Hewitt was born in Dubbo, Australia but spent most of his time in South Africa.
The trial continues.