What does "tough" mean?

Tough: Not easily broken; able to endure hardship; firm; strong; as, tough sinews. Cowper. A body made of brass, the crone demands, . . . Tough to the last, and with no toil to tire. Dryden. The basis of his character was caution combined with tough tenacity of purpose. J. A. Symonds.

Additional senses

  1. 2.Not easily separated; viscous; clammy; tenacious; as, tough phlegm.
  2. 3.Stiff; rigid; not flexible; stubborn; as, a tough bow. So tough a frame she could not bend. Dryden.
  3. 4.Severe; violent; as, a tough storm. [Colloq.] " A tough debate. " Fuller. To make it tough, to make it a matter of difficulty; to make it a hard matter. [Obs.] Chaucer.

Sources