The act of deceiving another. An action used for personal gain by lying to someone. If you tell are lie, and they believe you, you are deceiving them; deception.
The art of successfully using deception is a skill worth mastering if you know how to use it.
It's when you're doing a chick from behind and before you break off, you spit on her back (thereby 'deceiving' her into you thinking you are done) and then when she turns over, you blast her in the face.
"Hey Mom, I was banging this hot chick who was so uptight, I couldn't get off. In fact, the only way I could finish off was through 'deception.'"