In a sexual context this means only one thing: That man is promiscuous means that he has or desires frequent sex with a variety of partners. This a synonym for Sexually promiscuous.

Note that Sexually promiscuous does not mean "has lots of sex". A person could be happly married and have loads of sex, but would not be at all promiscuous. Quite the opposite.

However, promiscuous is not an exclusively sexual word, despite the preponderance of modern usage. But then, the preponderance of modern human interest is sexual.

The word's meaning is simply derived from the sum of its parts:
Pro: In favour of, exhibiting the caracteristic of
miscuous: pertaining to mixing.

Thus, anything that mixes a lot or is indiscriminate with whom it mixes is promiscuous, such as a promiscuous network card which reads packets irrespective of origin.