I've done HIIT as part of my strength workouts. It just refers to intervals of high-intensity mixed with rest periods, right? For ex, I've done a 20-min HIIT on a row machine; 2 mins warmup, 1 min fast speed, 1 min slow, 1 min faster, 1 min slow, 1 min faster again, 1 min slow, and so on. Or the treadmill: 2 mins warmup, 1 min speed 2, 1 min speed 3, 1 min speed 2, 1 min speed 4, 1 min speed 2, 1 min speed 5, 1 min speed 2.
I view it as short & sweet. I've read that it's more effective than stead-state cardio (like the treadmill or elliptical). I don't do it regularly, but keep thinking about doing 10-20 minutes of HIIT on my rest days from lifting.