Available Definitions:
1) superl. - Having the quality of flexibility without brittleness; yielding to force without breaking; capable of resisting great strain; as, the ligaments of animals are remarkably tough.
2) superl. - Not easily broken; able to endure hardship; firm; strong; as, tough sinews.
3) superl. - Not easily separated; viscous; clammy; tenacious; as, tough phlegm.
4) superl. - Stiff; rigid; not flexible; stubborn; as, a tough bow.
5) superl. - Severe; violent; as, a tough storm.