Rowdy or rough.
Harsh or severe.
Difficult or demanding.
Stubborn or persistent; capable of stubbornness or persistence.
Strong and resilient; sturdy.
Undergoing plastic deformation before breaking.
Difficult to cut or chew.
Rugged or physically hardy.
To endure.
To toughen.
Used to indicate lack of sympathy
A person who obtains things by force; a thug or bully.
Fickle.
Readily decomposable.
Not stable.
Radioactive, especially with a short half-life.
Unpredictable.
Having a strong tendency to change.
Fluctuating; not constant.
To release (an animal) from a stable.