1. an inflamation of a tendon.
2. a clever and shocking "nickname" to use when introducing a friend at a mexican restaurant. Meant to embarass said friend, confuse the waiter and provide years of future laughter at the thought.
waiter: "welcome to los dos amigos."
you: "hi, i am ryan. this is my girlfriend julia, and this is our friend tendonitis.
waiter: *walks away because he doesn't understand english and now you don't get any fucking tortillas*