Sentence:  Of course, there's also the holy Facebook trinity — wall posts, messages (it makes him feel like you're keeping a big secret, which sends the right message that you're not above being the secret <WSD>slam piece</WSD> on the side) and the coup de grace — pokes (which let him know you're not a prude and happy to make things physical). 
Meaning of the word marked with <WSD> tags:  A sexual partner with whom one has no particular emotional attachment.