safe sex

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Sexual activity with safeguards, such as a condom, used to avoid acquiring or spreading a sexually transmitted disease.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Sexual activity engaged in by people who have taken precautions to protect themselves against sexually transmitted diseases (STDs).

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun sexual activity (especially sexual intercourse) with the use of measures (such as latex condoms) to avoid the transmission of disease (especially AIDS)