CrossFit is defined as constantly varied functional movement executed at high intensity. It is a fitness program that is broad, general and inclusive by design. The aim is to improve your fitness by increasing your work capacity across broad time and modal domains.
We think this captures it pretty well:
“CrossFit is a cult, or a fitness movement, and possibly a sport. It could be all three, or if you throw in a lifestyle, all four. An all-encompassing open-source fitness movement involving gymnastics, Olympic lifting, aerobic work, and if the mood is right, whatever coach feels like putting on the website as the workout of the day. It is all done very quickly, and with great intensity, and if you are not prepared, it will kindly help you remember what you had for lunch by forcibly reintroducing it to you. If that doesn’t happen, then you will likely end up on the floor praying for oxygen.” — Spencer Hall
Wikipedia also has a good write-up:
“CrossFit is a strength and conditioning fitness methodology. Its stated goal is to create ‘the quintessential athlete: equal parts gymnast, Olympic weightlifter, sprinter, rower and 800 meter runner.’ CrossFit is not sport-specific and promotes broad and general overall physical fitness.”