(1):
(superl.) Not easily broken; able to endure hardship; firm; strong; as, tough sinews.
(2):
(superl.) Not easily separated; viscous; clammy; tenacious; as, tough phlegm.
(3):
(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.
(4):
(superl.) Stiff; rigid; not flexible; stubborn; as, a tough bow.
(5):
(superl.) Severe; violent; as, a tough storm.