Toughest

adjective

1. Strong and resilient; sturdy.

   "The tent, made of tough canvas, held up to many abuses."

2. (of food) Difficult to cut or chew.

   "To soften a tough cut of meat, the recipe suggested simmering it for hours."

3. Rugged or physically hardy.

   "Only a tough species will survive in the desert."

4. Stubborn.

   "He had a reputation as a tough negotiator."

5. (of weather etc) Harsh or severe.