The IAAF's medical commission, which begins meeting on Friday, could take a year to deliver that definition and its judicial commission will also be asked to consider future regulations, general secretary Pierre Weiss said on Saturday.
"We are obliged to react. It would have been better if we had been prepared to, but we were not prepared," Weiss said. "We will get a reply in the next 12 months - I don't expect anything to come out before. There is no definition, but it is the same in other sports - football, swimming, cycling. They don't have a definition."
The most common cause of sexual ambiguity is congenital adrenal hyperplasia, an endocrine disorder where the adrenal glands produce abnormally high levels of hormones.
"We were in Copenhagen (at the International Olympic Committee meetings last week) and I asked my colleagues from other sports if they had a definition and nobody has one," Weiss said. "But nobody (else) has had the problem so far."
Weiss expects the IOC medical commission to consider the same issue in November in Lausanne, Switzerland.
By the time Semenya won the 800 meters at the Berlin world championships in August, questions about the South African's gender had been raised after being sparked by stunning improvements in results coupled with her muscular build and deep voice.
Before the final, the IAAF announced it had ordered gender tests and it is still waiting for the final verdict from the experts on whether she can continue competing as a woman.
Weiss claimed not to have seen the test results, which reportedly show that Semenya has both male and female characteristics.
"They are being analyzed worldwide by experts," Weiss said. "We will promote the outcome of this case as soon as it is known. The plan is to make a deceleration at the latest during our council meeting in November."
Whatever the outcome, the 18-year-old Semenya is unlikely to be stripped of her medal or prize money, but the recriminations in South Africa are likely to linger.
The country's top athletics officials faced renewed calls for their resignations Friday from three provincial associations from the sport.
Athletics South Africa president Leonard Chuene has admitted he lied about his knowledge of the tests performed on Semenya in their country before the world championships.