Pegging.

[Misstress]

Pegging- Pegging is when a woman uses a strap-on dildo to penetrate her partner anally, usually a man. While this practice is not commonly mentioned due to the various taboos many cultures have against receptive male anal sex, and statistics are hard to come by, many people believe it is the most common use of strap-ons, and often manufacturers use images of a woman with a strapon and a male on the advertising or packaging for strap-on dildos and harnesses.
Pegging can be done for a variety of reasons, but probably the most common is that it allows a heterosexual male to receive anal pleasure. Both partners may enjoy pegging, and many men have an anal orgasm from it. Many people, such as advice columnist Dan Savage, believe all men should try pegging at least once, as it may introduce them to a new enjoyable sexual activity and illuminate them to the receiver's perspective in sex.
When pegging, even more than for other forms of anal sex, proper selection and quantity of lube is extremely important. Many dildos do not "hold" lube as well as a penis would, and a thicker or better adhering lube will likely perform much better.
A number of how-to videos about pegging have been made, for couples interested in trying it but not sure where to start, however most people feel a few minutes of experimenting to be plenty to learn the basic "ins and outs" of pegging.