I'm no expert, but to me, 'tactical' when it came to any genre meant it was made in a superior manner to the standard. Heavy duty, specialliy designed, lifestyle specific, or all of the above. With flashlights, careers that demand lighting in dark areas requires something more than a simple torch you'd stash in a drawer. Let's say, a police officer. He needs something for constant use, day after day, that will last enough to match his budget while giving off enough light to illuminate dark alleys, yards, houses, and in many cases it has to be bright enough to give one an advantage in dangerous situations. That's just performance. Odds are, if the companies went so far as to create something that performs, it also has to have handy little tricks for the most likely user. For instance, hexagonal rings to prevent rolling, filters, different designs of switches, holster compatibility and belt space, and even a clip so you can slap it on something.
When I was given my first light that had a clip, I just managed to smile and not roll my eyes. Great, it has a pocket protector clip, I sure use those a lot...
Now, every light, knife, multi-tool, and all my other other rugged gadgets have to have clips. Backpacking, tradework, home repair or construction, sperlunking, from extreme to simply out of the ordinary, I need the thing to stay attached to me. That's why most tact lights have clips. They're handy.
Now, let's say some guy with too much money bought a Mag accessory kit and put the anti-roll ring and the clip on his new Mini Mag, and maybe kept the red/bue filters in a drawer somewhere. Is it a tactical light? Not if it just takes up drawer space.
Now, let's say he used the MM base body. He put in a high-power LED, popped in state of the art cells instead of alkaline cheapies, even reworked the reflector and lens design, maybe even added a tail switch. And, of course, the roll ring and clip from the accessory pack. Sure, it is most definitely no Surefire, and it doesn't have 'TACTICAL!' bubble action bubbles all over it, it's superior to the average light, and is tailored to the user's purpose. I used the standard and somewhat gaudy mini Mag as a basic example, the same could be said for a Surefire or any high-ranking brand, I chose the standard model to demonstrate design compared to use.
Tactical, simply means to fulfill a specialized purpose. Most companies slap it on there to make the cop-wannabes and gearheads buy one to look like a SWAT member. Slap a clip on it, paint it black, whatever, but if it's just a drawer stuffer, it's not tactical. It's just more expensive. It's not what the box says, it's how you use it. Just ask those 'Wand Massager' companies.