Metcon doesn't have a strict definition. Its about intensity. Intensity is about power output over time. You might consider checking out the CFit Journal #31: Fooling Around With Fran. Fran has got to be one of the most painful metcon workouts because of the power output. It requires many of the things I mention below, not to mention stability and balance.
If i had to define metcon i would do it like this
1. High Heart Rate
2. Simultaneous Use of Many Muscles
3. Continuous Movement
4. Short to Medium Time (5-30 min)
and the best way to tell if your doing a metcon workout.....
YOU'LL KNOW IT !!!