Tough - adjective 1. strong and durable; not easily broken or cut. 2. not brittle or tender. 3. difficult to masticate, as food. 4. of viscous consistency, as liquid or semiliquid matter: tough molasses. 5. capable of great endurance; sturdy; hardy. I suppose I'm thinking more of number 5 when I think of humans being tough. They haven't backed down from any of the specied listed above despite being woefully mismatched at times and have even managed to come out on top at times despite the opposition. This is far more impressive than say some single minded drugged up Jem H'dar.