A metaphorical way of telling someone you are not bisexual and have no desire to hook up with that person. Can be used by either gay or straight people. Especially true if you are a baseball switch-hitter.
Bi person: Wanna play some ball? Those homers you hit from both sides of the plate really turn me on!!
You: Sorry, but I switch hit, but only in baseball!
You: Sorry, but I switch hit, but only in baseball!
by Stop the Pendulum April 8, 2006