Strong and resilient; sturdy.
Harsh or severe.
Difficult or demanding.
Stubborn or persistent; capable of stubbornness or persistence.
Undergoing plastic deformation before breaking.
Difficult to cut or chew.
Rugged or physically hardy.
Rowdy or rough.
Used to indicate lack of sympathy
To endure.
To toughen.
A person who obtains things by force; a thug or bully.
Capable of being shaped; malleable.
Easy to deal with or manage
Capable of being easily led, taught, or managed.
Sufficiently operationalizable or useful to allow a mathematical calculation to proceed toward a solution.
Algorithmically solvable fast enough to be practically relevant, typically in polynomial time.