Basically the phrase that embodies Wazzu's (Washington State) student population as a whole. Comes from their mascot: The cougar. It can mean anything from chokin during a sporting event (most likely) or can be used in a broad sense in that the Wazzu student is just being his/herself aka unintelligent ass-wipe.
"UW just beat Wazzu again for the Apple Cup. Haha, those morons are cougin it again."