At its most basic definition, exercise is sustained activity for a period of time. Intensity of the activity also comes into play—you can do a less intense activity for a longer period of time or a high-intensity activity for a short period (that’s where that whole 7-minute workout came from). So in theory, any physical activity you do could be considered exercise, if you do it for a sustained amount of time and with at least a moderate level of intensity.
Luckily, there’s a Compendium of Physical Activities that lists the MET values—one MET, or metabolic equivalent, is defined as one calorie per kilogram of body weight per minute, and is equal to sitting quietly—for pretty much everything. Typically 3 METs is the minimum for moderate exercise, or the value of a leisurely walking pace. Check out this list of 23 activities to see if they indeed count; we did the math to show calorie burn per half hour for a 165-pound man.