a sexual or romantic bandwagon; to be on the poon wagon means to be in a relationship or simply getting tons of ass. Typically a phrase used towards males.
Rodney: Hey man you've been hitting on her for weeks, just hop on the poonwagon already.
A non-coherant response, often giving as a reply when someone else says something extremely clueless or stupid, i.e. something that is not worthy of a real response. "Wagh" was coined by a Dane known as "Ignite"