(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.
(superl.) Not easily broken; able to endure hardship; firm; strong; as, tough sinews.
(superl.) Not easily separated; viscous; clammy; tenacious; as, tough phlegm.
(superl.) Stiff; rigid; not flexible; stubborn; as, a tough bow.