To engage in a romantic relationship with a person who is much better looking, and/or smarter, and/or in a higher socioeconomic class than you. Essentially, a person who is widely considered to be 'out of your league.'
Bob: Your new girlfriend is smokin' hot... A legitimate '8'... How do you continue to keep outkicking your coverage.
Other guy, also named Bob: I have an extremely large penis!
guy one: I had to break up with Vanessa.
guy two: Idiot! She was hot... Why??
guy one: I don't really want to admit it, but she outkinked me, man.
guy two: Can I call her?