(uncountable) The state of being tough / (materials science, physics, of a metal) Resistance to fracture when stressed / A formidable difficulty

plural of toughness

(of a material) Strong and resilient; sturdy. / (of food) Difficult to cut or chew. / (of a person or animal) Rugged or physically hardy.

(slang) Used to indicate lack of sympathy

A person who obtains things by force; a thug or bully.

To endure. / To toughen.

plural of tough

simple past tense and past participle of tough

present participle of tough

(mathematics) A measure, expressed by a positive integer (with the exception of complete graphs), of the connectivity of a graph.