molecular condom
n.— «For a decade now, scientists have been working to develop an HIV-blocking vaginal gel, a microbicide often called a molecular condom.» —“Better than a Condom?” by Jeneen Interlandi Newsweek Aug. 11, 2009. (source: Double-Tongued Dictionary)
Further reading
An Alabama man wonders about the verb to pooh-pooh, meaning to disdain or disapprove. It has nothing to do with the similar-sounding word for excrement, but rather the noise one makes when being dismissive. It started as simply pooh in the 1500s...
Gifts for book lovers: Martha recommends one for lovers of libraries and another for students of Spanish. Grant suggests some enchanting novels for young readers. When it comes to books, though, you can’t always judge them by their original titles...