a. Having a sudden sensation, upon meeting an incredibly douchey person, of feeling a rift in space-time, whilst thinking you've met this person before.
b. An obnoxious individual who seems to cheaply imitate the swag of someone you know.
Jenn: (whispers) Doesn't this guy remind of Bobby?
Trish: (whispers back) Yeah, I'm totally having douche-a vu right now.
Jenn: Me too!