Sexual activity that is completely free of risk for STD. It is non-existent.
measures taken to reduce the risk of acquiring a sexually transmitted disease, such as the use of a condom
Sexual intercourse conducted in such a way as to NOT exchange bodily fluids that might carry infection. Method 1: With partners you are unsure about use barriers such as condoms. Method 2: Have your partner tested and see their lab results. In my medical practice I commonly test couples for sexually transmissible diseases before they move on to sexual intercourse without condoms. This method relies on trusting your partner's fidelity and so is less reliable than always using barriers.